Chemical And Biochemical Physics: New Frontiers

CHEMICAL AND BIOCHEMICAL PHYSICS: NEW FRONTIERS

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CHEMICAL AND BIOCHEMICAL PHYSICS: NEW FRONTIERS

G. E. ZAIKOV EDITOR

Nova Science Publishers, Inc. New York

Copyright © 2006 by Nova Science Publishers, Inc.

All rights reserved. No part of this book may be reproduced, stored in a retrieval system or transmitted in any form or by any means: electronic, electrostatic, magnetic, tape, mechanical photocopying, recording or otherwise without the written permission of the Publisher. For permission to use material from this book please contact us: Telephone 631-231-7269; Fax 631-231-8175 Web Site: http://www.novapublishers.com NOTICE TO THE READER The Publisher has taken reasonable care in the preparation of this book, but makes no expressed or implied warranty of any kind and assumes no responsibility for any errors or omissions. No liability is assumed for incidental or consequential damages in connection with or arising out of information contained in this book. The Publisher shall not be liable for any special, consequential, or exemplary damages resulting, in whole or in part, from the readers’ use of, or reliance upon, this material. Independent verification should be sought for any data, advice or recommendations contained in this book. In addition, no responsibility is assumed by the publisher for any injury and/or damage to persons or property arising from any methods, products, instructions, ideas or otherwise contained in this publication. This publication is designed to provide accurate and authoritative information with regard to the subject matter cover herein. It is sold with the clear understanding that the Publisher is not engaged in rendering legal or any other professional services. If legal, medical or any other expert assistance is required, the services of a competent person should be sought. FROM A DECLARATION OF PARTICIPANTS JOINTLY ADOPTED BY A COMMITTEE OF THE AMERICAN BAR ASSOCIATION AND A COMMITTEE OF PUBLISHERS. Library of Congress Cataloging-in-Publication Data Chemical and biochemical physics : new frontiers / G.E. Zaikov, editor. p. cm. Includes index. ISBN: 978-1-60876-244-6 (E-Book) 1. Chemistry, Physical and theoretical. 2. Physical biochemistry. I. Zaikov, Gennadii Efremovich. QD453.3.C44 2006 541--dc22 2006010331

Published by Nova Science Publishers, Inc. New York

CONTENTS Preface

vii

Chapter 1

Nikolai M. Emanuel is the Phenomenon in Science S. B. Varfolomeyev and G. E. Zaikov

1

Chapter 2

Scientific Ideas of Academician N.M. Emanuel and Modern Science E. B. Burlakova and G. E. Zaikov

9

Chapter 3

Energy of Chemical Bond and Spatial-Energy Principles of Hybridization of Atom Orbitals G. А. Коrablev and G. E. Zaikov

Chapter 4

Preparation and Application of Magnetic Adsorbents in Biological and Medical Investigations E. K. Dobrinskiy, S. I. Malashin, V. G. Gerlivanov, G. V. Stepanov, V. I Filippov, L. Kh. Komissarova, L. A. Goncharov, F. S. Bayburtskiy, T. V. Tsyganova and H. U. Lubman

Chapter 5

The Magnetic Sorbents Used for Detoxification of Blood N. P.Glukhoedov, M. V. Kutushov, M. A. Pluzan, G. V. Stepanov, L. Kh. Komissarova, V.I. Filippov, L. A.Goncharov, F.S. Bayburtskiy

Chapter 6

Influence Hexsaazocyclanes on a Microstructure of Polyethylene Terephthalate O. V. Burykina and F. F. Nijazi

Chapter 7

Functionalising of Low-Molecular, Oligomer Dienes and Olefins with S, O-Containing Compounds R. Z. Biglova, A. U. Galimzjanova V. A. Dokichev, G. V. Konesev, G. E. Zaikov, R. F. Talipov

Chapter 8

Fractal Model of Stability to the Cracking of Modified Polyethylene A. Kh. Malamatov and G.V. Kozlov

Chapter 9

The Theoretical Description of Modified Polyethylene Thermostability within the Framework of Anomalous Diffusion Models A. Kh. Malamatov and G.V.Kozlov

13

29

41

47

53

67

73

vi Chapter 10

Chapter 11

Chapter 12

Contents Quantum-Chemical Calculations of Analysis Reactivity S-and O-Annes, Generated from 6-Methyl-2-Thio-, 2-Alkyl(Aralkyl)Thiouracils A. I. Rakhimov, E. S. Titova, R. G. Fedunov, V. A. Babkin, G. E. Zaikov Mathematical Models of Tumor Processes and Strategies of Chemotherapy Yu. A. Ershov and V. V. Kotin One-Stage Method of Catalytic Oxidation of Vegetal Raw Materials by Oxygen: Novel Ecologically Pure Products and Perspectives of Their Practical Use A. M. Sakharov

Chapter 13

EPR-Spectroscopy of Complex Polymer Systems A. M. Wasserman and M. V. Motyakin

Chapter 14

Organosilicon Copolymers with Carbocyclosyloxane Fragments in Dimethylsiloxane Backbone O. Mukbaniani, G. Zaikov, N. Mukbaniani and T. Tatrishvili

Chapter 15

Organosilicon Oligomers and Copolymers of Bead-Shaped Structure O. Mukbaniani, G. Zaikov and T. Tatrishvili

Chapter 16

Organosilicon Copolymers with Monocyclic Fragments in the Main Dimethylsiloxane Backbone O. Mukbaniani, G. Zaikov and T. Tatrishvili

Index

79

87

113 127

149 167

217 263

PREFACE «Dissemination of education means spreading of prosperity. I mean universal rather than private wealth. Prosperity is the only thing that will eliminate the most (significant) part of Evil.» Alfred Nobel Stockholm, Sweden «Be brave and use your mind.» I. Cant Koeniksberg, Germany

It’s a pity that Nikolai M. Emanuel has not lived up to his current anniversary. He died at 69 years old (October 1, 1915 – December 8, 1984). He was a remarkable scientist and an outstanding administrator of science (refer to Chapters 1 and 2 of the current manuscript). In this Collection, we discuss problems of chemical physics and biochemical physics. As a branch of science, chemical physics was established in the first three decades of the 20th century by some famous scientists (including the Nobel Prize Laureate, Academician Nikolai N. Semenov − the founder of the Institute of Chemical Physics, Academy of Sciences of the USSR). Biochemical physics, on the other hand, representing the area of knowledge at the junction of three natural sciences, was created in the middle of the 20th century. The leader of this creation was Academician N.M. Emanuel − the founder of the Institute of Biochemical Physics, Russian Academy of Sciences. N.M. Emanuel managed to apply the knowledge accumulated in the branches of chemistry and physics to solving problems in biology, medicine and agriculture. In this Collection we tried to gather new original articles of some students of N.M. Emanuel and corresponding reviews. These articles show current developments of the ideas, once spoken about by N.M. Emanuel in his works, at seminars, and at conferences. Prof. G. E. Zaikov (the student of Academician N.M. Emanuel)

In: Chemical and Biochemical Physics: New Frontiers ISBN 1-60021-165-8 Editor: G. E. Zaikov, pp. 1-8 © 2006 Nova Science Publishers, Inc.

Chapter 1

NIKOLAI M. EMANUEL IS THE PHENOMENON IN SCIENCE S. B. Varfolomeyev∗ and G. E. Zaikov N. M. Emanuel Institute of Biochemical Physics; Russian Academy of Sciences; Moscow, Russia

"Everything is afraid of time. And only time is afraid of pyramids" Proverb. Ancient Egypt

When successors write anniversary notes about the teacher who was a scientist they like to bear in the title such words as "outstanding", "world famous", "unique", etc. It seemed to us, that in the case of Nikolai M. Emanuel all this is not enough. For this reason we have decided to place there a word "PHENOMENON". A painting by Ivanov from the Tretyakov Gallery collection, "The Appearance of the Christ to the People," comes to mind in this case where people are overwhelmed and filled with admiration by this phenomenon. People and colleagues who worked with Nikolai M. Emanuel feel much the same as the people from the Ivanov painting. We have to confess, that this word was not thought up by us, but by Nikolai M. Emanuel, having said it on April 16th, 1981 during a meeting devoted to the 85th anniversary of his teacher - academician Nikolai N. Semenov. Nikolai N. Semenov, in addition to being a Nobel Prize winner, was the organizer and permanent director of the Institute of Chemical Physics (ICP) of the Academy of Sciences of the USSR (AS USSR) in the period between 1931 and 1986. Both Semenov and Emanuel (as well as many other scientists) have glorified our country and have helped usher in huge contributions to the development of science and practice. N. M. Emanuel was a physicist by education, but he worked not so much in physics, but in chemistry, biology and even medical science. He taught us that it is highly undesirable to be engaged for long time in the same field of science, and it’s better to periodically change ∗

[email protected]; [email protected]

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S. B. Varfolomeyev and G. E. Zaikov

our direction of scientific activity. This will allow to use the accumulated knowledge in new areas of science. Many of Emanuel’s colleagues did not wish to change the structure of their work nor become engaged in something new (polymers instead of low-molecular compounds or biology instead of chemistry). “We know nothing in this new area”, they exclaimed. “Fine!” he answered. “You are not burdened by the dogmas of that field of science which you’re entering, and the basics of this area you can find in books”. A conclusion: Nikolai M. Emanuel was an innovator and he called for others to be the same. One who works for a long time in the same narrow field of science involuntarily “levels off” and the probability that he/she will make something outstanding is very little. Usually in such cases scientists work by a principle, “from N to N+1”. Unfortunately, N. M. Emanuel died early at age of 69 years, 2 months and 7 days. He was full of a creative power, energy and new plans when he suddenly left us. It had occurred on December, 8th, 1984 in ICP branch in Chernogolovka (Moscow suburb) in his business apartment on Saturday. He was home alone preparing a report on an agriculture topic for a meeting on Monday, December 10th, with the General Secretary of the Central Committee of the CPSU1, M. S. Gorbachev. Suddenly, he felt badly and had called for an ambulance which quickly arrived. However, physicians did not have any medicines and they only checked-up Nikolai Emanuel, but failed to help. He died from a heart attack. One relaxation shot would have quelled the painful shock and his heart would not have failed, but those were times when nothing could be bought. Citizens of our country “did not buy things” those days, but “got them found”. The verb “to buy” has gone out of use and it has been replaced by the verb “to find” (for example, “I’ve found it!”). There was such joke those days, named “Paradoxes of Socialism”. Here is a chain of events describing it: “Nobody works in the country, but the plan is fulfilled and exceeded. The plan is fulfilled and exceeded, but grocery stores are empty. Grocery stores are empty, but people have plenty of food at home. People have plenty of food at home, but everyone is dissatisfied. Everyone is dissatisfied, but all together vote in favor of Socialism”. Nikolai Emanuel has died because there were many paradoxes in our country those days. Even at the end of his life, Nikolai Emanuel had time to promote worthy representation of our science at the International level. He was the head of the National Committee of the Soviet Chemists and he earned great respect among scientists in the International Union of Pure and Applied Chemistry (IUPAC). The IUPAC Executive Committee had long ago decided to elect Nikolai Emanuel as Vice-president of the Union (in two years he would automatically become a President of IUPAC, and in two years - Past President) on IUPAC General Assembly in 1985. All application documents for a position of Vice-president had to be submitted to IUPAC Headquarters in Oxford (England) till December, 25th, 1984. The situation seemed so clear that nobody but Nikolai Emanuel submitted documents in Oxford. And suddenly, Nikolai Emanuel passed away. The overwhelming majority of National Committees of the various countries found out about it very late and nobody had time to prepare the documents. Only the National Committee of the Soviet Chemists had quickly presented to Oxford documents on the Member of the Central Committee of the CPSU, Vicepresident AS USSR and the President of the Siberian Branch of AS USSR, an academician, Valentin Afanasevich Koptyug. In spite of the fact that in the moment prior to his death Nikolai Emanuel was the only Academician-Secretary of Branch of the General and 1

Communist Party of Soviet Union

Nikolai M. Emanuel is the Phenomenon in Science

3

Technical Chemistry (BGTC) AS USSR, his influence at the International level was incomparably greater than of Valentin Koptyug. Since other countries did not practically have a chance to nominate anybody, Koptyug had been elected by “a socialist variant” - one candidate per one vacant place. Now we’ll turn to Nikolai Emanuel's biography since this article is written to commemorate his 90th birthday. He was born in Tima, a town in the Suburb of Kursk. He began work in ICP in Leningrad, in 1938. He had proven himself as a talented young scientist in the field of kinetics, and he possessed a characteristic work-style which was traced from the beginning of his scientific work and distinguished him on all subsequent ways of scientific creativity. His first project devoted to oxidation kinetics of hydrogen sulphide was of great importance for the development of the theory of branched out chain reactions in a gaseous phase. With the beginning of Great Patriotic War, he had left to defend his Motherland and battled in Estonia. Under the decision of the country leaders, talented scientists (those who were not killed in battles in the first months of war) were demobilized and relocated in the research centers to help the troops in carrying out applied research. In 1942, soon after demobilization from the army, he had defended his PhD thesis on the theme, “Oxidation of Hydrogen Sulphide”. He generalized this research in the book “Intermediate Products of Complex Reactions in Gaseous Phase (Moscow-Leningrad, Publishing house AS USSR, 1946) where, for the first time, it has been shown that such intermediate products as sulfur oxide possess properties of free radicals and can propagate oxidation. It was an important scientific benchmark. Since 1944 Emanuel supervised over the Laboratory of Kinetics of Intermediate Substances in ICP (Moscow) which in 1956 had been renamed into Laboratory of Oxidation of Organic Substances. In 1949 he had defended the thesis for a Doctor of Sciences degree, and had received a professor rank in 1950. Nikolai Emanuel always aspired to develop those directions in a science which were important at the present moment and could enrich not only fundamental science, but also bring a practical advantage of implementation. Since 1954 he supervised works on kinetical research and the mechanism of oxidation of hydrocarbons and other organic substances in a liquid phase. As a result of this research, the chain theory of liquid-phase oxidation of organic substances has been created and experimentally proved, and a number of original methods of synthesis of important chemical products have been proposed. A Moscow oil refinery in Kapotnya, manufacturing 10,000 ton/year of acetic acid and methylethylketone by liquid-phase oxidation of normal butane under conditions close to critical has been built. Together with the French company RhonePoulenc, pilot reactors on liquid-phase oxidation of propylene in propylene oxide – an initial raw material for polyurethane synthesis and rocket solid fuel - have been constructed on the basis of Nikolai Emanuel's ideas in Leon’s suburbs (France). The shop on oxidation of paraffins with production of laundry liquids has been created on Shchebekino chemical plant. Most importantly, between 1950-1960 N. M. Emanuel had became a world-recognized scientist. He was known by everyone who worked in the field of chain reactions, oxidation, chemical kinetics and chemical physics in general. In 1958 Emanuel was awarded the Lenin Prize in chemistry and the same year he was elected as a member-correspondent of AS USSR for works in the field of properties and features of chain reactions. In 1966 he had been elected as a full member of the AS USSR.

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S. B. Varfolomeyev and G. E. Zaikov

The works executed under direction of Nikolai Emanuel in the field of ageing and stabilization of polymers have large practical value. He headed this research not only in ICP where more than 10 laboratories (180 scientists) worked on the given subjects, but also in the AS USSR and in the Academies of Union Republics, within the Committee on the Science and Techniques, and in cooperation of Academies of Sciences of the Socialist Countries and the Council of Economic Mutual Aid. Nikolai Emanuel was more then just a fine scientist able to perform out-of-the-box thinking. He was also a unique manager of science. He appreciated in his successors an ability to think both as a scientist and as a manager. Now allow us to step a little away from the basic text of this article in area of lyrical reasoning. At first Nikolai Emanuel did not have such good relations with academician Valentin Alekseevich Kargin who headed polymer science in our country. It wasn’t until 1966 when they went on a business trip together that they became friends. Valentin Kargin was aware of Emanuel’s work on oxidation of organic compounds and suggested that Nikolai Emanuel personally head works on ageing and stabilization, and then on polymers’ flammability. ICP settled down earlier to the address of: Moscow, Vorobevskoe highway, 2B (Institute of Physical Problems of academician Peter Leonidovich Kapitsa was at Vorobvskoe highway, 2), while Soviet Prime-Minister Alexey Nikolaevich Kosygin resided at Vorobevskoe highway, 6 (N. M. Emanuel resided in the same street in building number 4). Each time there were elections in our country, Alexey Kosygin came to ICP building 1 for participation in the election. Obviously, during the same moment, all (or almost all) heads of the Academy of Sciences were there. Nikolai Emanuel was there too. As a rule, after voting, Alexey Kosygin followed academician N. N. Semenov (ICP director) to his office where perfect cognac and fine food were served and informal conversation about USSR development took place. Further, we simplify real events only to keep this article short. There once was such a dialogue: Alexey Kosygin addressed Nikolai Emanuel and said, “Nikolai Markovich! Why does our industry make such poor-quality polymeric products? It’s so easy to distinguish the quality of our polymeric film from a foreign one”. Nikolai Emanuel responded, “Because you have bought polymer technology plants abroad and have constructed a number of plants, but we do not have industry to manufacture stabilizers for polymers, and often our industry makes polymeric products without stabilizers”. А. K.: “What is stabilizer?” N. E. describes to А. K. the essence of a problem. А. K.: “What do we have to do? What can you propose?” N. E.: “Let's solve the problem for a whole country. I suggest constructing a building for Polymer Stabilization on a site of Moscow Trust of Green Plantings that is located between Semenov and Kapitsa institutes. We’ll hire scientists and we shall solve this problem both theoretically and practically with the creation of industrial production of Soviet stabilizers”. Alexey Kosygin had taken a sheet of paper and had written: “To Slavsky (one of the Ministers) - to construct the building of Polymer Stabilization in an area of 10000 m2. To Kostandov (Minister of the Chemical Industry) and Fedorov (Minister of the Petrochemical Industry) - to allocate financing for construction of the building. Complete construction by

Nikolai M. Emanuel is the Phenomenon in Science

5

1975”. However, as we all know, it’s hard to implement something in time. Construction had been completed only in 1985 by which time Nikolai Emanuel had already passed away. When Emanuel passed away there were academicians and other “supervising comrades” who declared that there is no such scientific problem as the ageing of polymers, but rather some practical problems for handicraftsmen instead of for true scientists. Apparently, those “representatives from a science” were not familiar with the journal, Polymer Degradation and Stability, published in Oxford publishing house Elsevier, which has one of the greatest citation indexes in scientific literature. Throughout 25 years there has always been one of Emanuel’s successors on the editorial board of this journal. Now, when such research in our country is recognized as having no perspective, our representatives in this journal are not present. Yet, there are more and more scientists from China, South Korea, Japan, India and Malasia, along with scientists from the USA and Western Europe. Nevertheless, the manufacturing of stabilizers (PHENOZANs) in our country was created by the efforts of Nikolai Emanuel and his co-workers (V. V. Ershov, G. A. Nikiforov, A. A. Volodkin and many others). PHENOZAN means PHENOls from a plant (“Zavod” in Russian) and Academy of Sciences (“Nauk” in Russian). The first production has been started up in Kapotnya. There were more manufactures, but most of them have come to be in the foreign countries after USSR disintegration. Under the direction of Nikolai Emanuel, forecasting criteria for stability of polymeric products in conditions of their manufacturing and storage were developed, mechanisms of polymers’ ageing were discovered, the quantitative description of these processes was developed, new mechanisms of polymeric materials flammability reduction were proposed, the new generation of antipyrenes was created, etc., etc. N. M. Emanuel was one of the founders of a new direction in science – physico-chemical biology. He proposed for the first time to use inhibitors of radical reactions (antioxidants and bioantioxidants) as anti-tumor and radioprotective agents. His successors, E. B. Burlakova and D. B. Korman, provided invaluable help to him in these works. When Nikolai Emanuel visited USA or Western Europe with reports on these themes in 1960 - 1970, other chemists quietly chuckled at him: “he is a physicist by education and a chemist by soul – what is he doing in biology and medicine? It’s not chemistry where everything is much easier”. However, years went by and today if you go into any drugstore worldwide you will find bioantioxidants - vitamin E (spatially hindered phenol) - or tocopherol (4 isomers). Now they do not like to recollect (and do not recollect) who has taught them. N. M. Emanuel was teaching in a sub-department of Chemical Kinetics at the Department of Chemistry at M. V. Lomonosov Moscow State University. From the moment of the foundation of the sub-department of Chemical Kinetics in December, 1944 he was the assistant to the Chair - N. N. Semenov – and he gave annuall lectures on chemical kinetics, supervised over scientific work of young scientists, post-graduate students and students carrying thesis research. He had written a textbook, “A Course of Chemical Kinetics,” (Moscow, “Vysshaya Shkola”, 1962) with academician Dmitry Georgievich Knorre (professor then), which has already sustained 4 editions and been translated into foreign languages. Academicians, members correspondents, and doctors of sciences and philosophy are among his successors, a few hundreds in total. The works of Nikolai Emanuel have received world recognition. His lectures and reports, which have been given in different countries of the world (USA, Canada, the Western Europe, Japan, China, etc.), were very popular.

6

S. B. Varfolomeyev and G. E. Zaikov

He had been selected as a full member of many Academies in the world, including New York Academy of Sciences (USA), a foreign member of the Swedish Royal Academy of Sciences, a doctor Honoris Causa of the Seged University (Hungary), a honorary member of the Hungarian Academy of Sciences, a member of the German Academy of Scientists “Leopoldina” (GDR2), a foreign member of the Academy of Sciences of GDR, an honorary doctor of sciences of Uspal university (Sweden), etc. N. M. Emanuel began his scientific-organizational activity in 1942 when ICP was in Kazan city. For many years he was a scientific secretary of ICP, and then a Science Deputy Director. Nikolai Emanuel was an academician-secretary of BGTC AS USSR from 1975 and up to the end of his days. For many years he was the editor-in-chief of “Uspekhi Khimii” journal and a member of editorial boards of many domestic and foreign journals, including industrial editions. In 1971 Nikolai Emanuel had been selected as a member of the Bureau and Executive Committee of IUPAC and he was a chairman of the National Committee of the Soviet Chemists. N. M. Emanuel – was the hero of socialist work, the winner of Lenin and State prizes, A. N. Bah premiums, the author of many monographies published in our country and abroad, and hundreds of reviews and original articles, the author of the registered discoveries. He has many awards and medals from the USSR. More than twenty years have passed since Nikolai Emanuel left us. There will not be enough pages in this article nor in the entire “Bulletin of AS” journal to describe all that was done by N. M. Emanuel for science. Everything he made for science has already entered deeply into the consciousness of his successors and is reflected in the foundation of a new scientific institute of the Russian Academy of Science - Institute of Biochemical Physics carrying the name of Nikolai Markovich Emanuel (IBCP of the Russian Academy of Sciences). This Institute has been created by order #227 (1994) of Presidium of the Russian Academy of Sciences “for development of fundamental research of physical essence of chemical processes in the biological and molecular-organized chemical systems”. In 1995 IBCP of the Russian Academy of Science was awarded by name of academician N. M. Emanuel. The first director of IBCP was academician Alexander Evgenevich Shilov (scientific supervisor of IBCP now), and the first deputy director on scientific work was professor Elena Borisovna Burlakova, who carries this duty these days. N. M. Emanuel was a cheerful person and, despite the many years since his passing, we still feel pain over the loss. There lives a grateful memory in those who were his friend, colleague or student. Three monographies will be published by Nikolai Emanuel's 90th birthday. One of them is N. M. Emanuel's selected works (Moscow, “Nauka”, 2005). Two others are reviews of his students and successors where they’ll show how N. M. Emanuel’s ideas have worked in his students’ and followers’ works for the last 20 years, in the English (Brill Academic Publishers, Leiden, The Netherlands, 2005) and Russian (Moscow - Ufa, “Khimiya”, 2005) languages. We’d like to finish this article with something informal. We recall that Nikolai Emanuel often went to the Department of Science and the Department of Chemistry of the Central Committee of the CPSU in Moscow downtown where he defended new scientific projects and 2

German Democratic Republic

Nikolai M. Emanuel is the Phenomenon in Science

7

new budget. Sometimes he was successful, sometimes he was not. Once, when he had returned to work full of negative emotions (he was not successful that time), he told that he had deduced the mathematical formula which describes our country, and, more precisely, a management of our country. In his opinion (for that moment), all this was described by a square root of minus one. Unfortunately, Nikolai Emanuel is no longer with us, and we do not know how to describe mathematically the attitude to a science of a present management of our country. Nikolai Emanuel was able to gather both young and mature scientists around him. Among the mature ones are members-correspondents AS USSR Iosif Abramovich Rappoport and the professor Lev Alexandrovich Blumenfeld, who worked in Emanuel’s department for many years. Among the young ones is Mikhail Arkadevich Ostrovsky (an academician of the Russian Academy of Sciences these days). Mikhail Ostrovsky was a timid young man who did not know, really, the dark side of life. Once there was a meeting where Nikolai Emanuel had told to everyone (including Ostrovsky): “We have to let Ostrovsky feel anger!” He wanted that Mikhail Ostrovsky understand a sense of real life as well. There were/are many co-workers and colleagues who worked with Nikolai Emanuel for years. We have already mentioned some of them in this article, but here we shall mention more. Here we wish to name Zynaida K. Majzus, Erna A. Blumberg, Tatyana E. Pavlovskoj, Ilya V. Berezin, Kira Е. Kruglyakova, Irina P. Skibida, Dmitry J. Toptygin, Lana P. Lipchina, Igor I. Sapezhinsky, Lyudmila S. Evseenko, Kirill M. Dyumaev, Leonid D. Smirnov, Georgy P. Gladyshev, Anatoly L. Buchachenko, Eugeny T. Denisov, Jury A. Shljapnikov, Victor Y. Shlyapintoh, Tatyana E. Lipatova, Rostislav F. Vasil’ev, Alevtina B. Gagarina, Lora B. Gorbacheva etc., etc. The full list should include 700 - 800 names. Hope the others will forgive us for not including everyone in this list Nikolai Emanuel was very glad and proud that his ICP department had (and still has) a vivarium with mice and rats. As it’s well known, the introduction of even one new medication in a clinical practice requires performing tests to reveal side effects, and that requires about 10 years of experiments. Nikolai Emanuel had introduced a number of anti-tumor medications in health care. There was/is a chemical-therapeutic building in the 2nd city hospital where his medications were tested after numerous approvals. We do not know whether he had thought this up himself or if someone told it to him, but once he told us this joke-riddle: Question: “Tell me, please, is communism a science or an art?” Answer: “Communism is an art” Question: “And why?” Answer: “Because, if it was a science, it would be tested on mice and rats first” Nikolai Emanuel tested his medications on animals and was proud that he did it himself. In some topics Nikolai Emanuel was not able to show persistence and win the battle. Nikolai Emanuel liked to drive his “Volga”. And once he was stopped by a GAI3 officer by the subway station, “Leninskie Gory”. Nikolai Emanuel went out of his car and began to explain what happened, and the officer was unmerciful and demanded the penalty. Luckily, one of Nikolai Emanuel’s employees, Leva Aramovich Piruzyan, drove by (now he is an academician of the Russian Academy of Sciences). He saw that Nikolai Emanuel was in trouble and needed help. Now almost everyone has a mobile phone, but those days only KGB officers and other high-ranked officials had portable phones. Leva Piruzyan has taken an 3

State Automobile Inspection, i.e. road patrol/police

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S. B. Varfolomeyev and G. E. Zaikov

ordinary desk phone from his office and has put it in his car “Volga”. Obviously, the phone was not connected and did not work as a communication device. However, passing by GAI officers with excessive speed, he picked up a telephone tube and shouted. “The First listens!” It used to create a terrifying effect. GAI officers saluted him with no questions asked. So, he passed Nikolai Emanuel and the GAI officer slowly and shouted again, “The First listens!”, and then he jumped out of his car and ran up to the GAI officer, asking, “What are you doing?!?” The GAI officer was surprised. “What’s a problem?” Piruzyan had whispered, as it was a secret, “you keep ‘closed’4 academician on the open place. Release him immediately”. The GAI officer was frightened. He apologized and let them go repeating “sorry, sorry”. Tatyana E. Pavlovskaya, the wife of Nikolai Emanuel, had been by him all his life. She has been a researcher. However, she had enough forces to create a comfort for Nikolai Emanuel that allowed him to work successfully. Their daughter, Olga Nikolaevna Emanuel, holds a PhD degree in Chemistry. She works in N. M. Emanuel IBCP. Great Russian/Soviet poet, Vladimir Vladimirovich Mayakovsky, wrote that the memories of outstanding people live in the names of cities, libraries, universities, etc. In the case of N. M. Emanuel, this is true twice: IBCP carries his name first, and second, all his scientific ideas live in the developments of his successors. His life goes on!

4

‘Closed’ people were/are carriers of state secrets, i.e. they were forbidden (‘closed’) to be exposed to other people

In: Chemical and Biochemical Physics: New Frontiers ISBN 1-60021-165-8 Editor: G. E. Zaikov, pp. 9-11 © 2006 Nova Science Publishers, Inc.

Chapter 2

SCIENTIFIC IDEAS OF ACADEMICIAN N. M. EMANUEL AND MODERN SCIENCE E. B. Burlakova∗ and G. E. Zaikov Emanuel Institute of Biochemical Physics, Russian Academy of Sciences, Moscow, Russia "Gratitude is associated solely with bees and their gratitude is sweet." Sherlock Holmes Sir Arthur Conan Doyle

Usually, Sherlock Holmes was right in his conclusions and assessment of situations while applying his deductive method of analysis. However, in this case, his ideas do not work.. Our country (the USSR successor), Russian scientists, the world scientific community, followers, friends, and colleagues of Academician N.M. Emanuel, and all who knew and worked with him are grateful to him and keep dear memory of him. On October 1, 2005, we commemorated the 90th anniversary since the birthday of Nikolai Markovich. The Russian Academy of Sciences, the Department of Chemistry and Science of Materials, the Emanuel Institute of Biochemical Physics, the Semenov Institute of Chemical Physics, the Institute of Problems of Chemical Physics (Chernogolovka, Moscow Region), and the Faculty of Chemistry of Lomonosov Moscow State University commemorated the date and held a conference dedicated to the memory of Academician Emanuel. The title of the Conference, Scientific Ideas of Academician N.M. Emanuel and Modern Science, is significant because Nikolai Markovich put forward many scientific ideas and hypotheses, which were developed later in modern science. The Organizing Committee of the commemoration events and Conference included Academician N.A. Plate (Chairman, Vice-President of the Russian Academy of Sciences), Academicians V.A. Kabanov (Vice-Chairman), S.M. Aldoshin, M.V. Alfimov, A.I. Konovalov, V.V. Lunin, O.M. Nefedov, M.A. Ostrovskii, L.A. Piruzyan, and A.E. Shilov, Corresponding Members of the Russian Academy of Sciences K.M. Dyumaev, G.B. Manelis,

∗

e-mail: [email protected]

10

E.B. Burlakova and G.E. Zaikov

and V.F. Razumov, Drs. of Science E.B. Burlakova, A.A. Popov, S.D. Varfolomeev, and G.E. Zaikov, and Ph.D. V.P. Balakhnin. On September 30, 2005, a special session of the Scientific Council of the Moscow State University dedicated to the memory of Emanuel was held at the Faculty of Chemistry. Academicians V.V. Lunin (Dean), N.A. Plate, V.A. Kabanov, A.L. Buchachenko, I.P. Beletskaya, and Professors E.B. Burlakova and M.Ya. Melnikov spoke with recollections about Nikolai Markovich and his role in the development of Soviet science and education of young generations. On October 3, 2005, the scientific conference was opened at the Emanuel Institute of Biochemical Physics. Academician Plate delivered the opening speech. Professor Varfolomeev (Director) spoke about significant facts of life and scientific achievements of Emanuel; Dr. M.R. Lechinitser emphasized the importance of theoretical works of Emanuel for the formation of clinical oncology. Academicians V.A. Kabanov, A.E. Shilov, A.A. Berlin, K.M. Dyumaev, L.A. Piruzyan, G.B. Manelis, and L.V. Zabelin participated in the scientific discussion that took place at the session. The 2nd session of the Conference was held at the Institute of Problems of Chemical Physics (Chernogolovka) on October 4. The opening lecture was delivered by Academician S.M. Aldoshin (Director). This session included four presentations. Professor N.P. Konovalova reported on antioxidants and donors of nitrogen monoxide (antitumor effects of nitroxides and NO-donors); the report of N.A. Sanina and S.M. Aldoshin was concerned with a new class of NO-donors (synthesis, structure, properties, and practical use of sulfur-nitrosyl complexes of iron). Free-radical mechanisms of induction and development of secondary necrosis after gun wounds were the subject of the lecture by G.N. Bogdanov; L.D. Smirnov reported on pharmacological properties and promising clinical application of antioxidants of the heteroaromatic array. The 3rd session of the Conference (Oct. 4) included five presentations. The report by E.T. Denisov on the radical chemistry of artemisinine aroused great interest in the audience. The report by L.A. Ostrovskaya and D.B. Korman dealt with the use of nitrosoalkylurea in the antitumor chemotherapy. Special effects of peroxide oxidation of lipids of biological membranes in the presence of ultra-low concentrations of antioxidants were reported by N.P. Palmina; the report by L.B. Gorbacheva was devoted to biochemical studies on chemotherapy. L.K. Obukhova spoke about mechanisms of ageing of organisms and feasibility of lifespan prolongation. The 4th and 5th sessions of the Conference were held on October 5 at the Emanuel Institute of Biochemical Physics. The 4th session included seven reports. Dr. G.E. Zaikov presented the information about the latest achievements on reduction of inflammability of polymer materials and the use of nanocomposites as antipyrenes (substances that reduce the inflammability of polymer materials); Dr. A.A. Popov reported on the kinetics of destruction of strained polymers (strained molecules reactivity). The structural and dynamic parameters of interfacial layers in filled polymers were the subject of the report by A.L. Kovarskii and T.V. Yushkina; the report by G.B. Pariiskii, I.S. Gaponova, E.Ya. Davydov, and T.V. Pokholok dealt with the studies on mechanisms of generation of stable nitrogen-containing radicals in the presence of nitrogen oxides. Great interest was aroused by the report of a group of authors (Academician Yu.B. Monakov, Yu.S. Zimin, and V.D. Komissarov) on the kinetics and mechanism of ozonized oxidation of ketones. The work by V.A. Kuzmin, P.P. Levin, and A.S. Tatikolov contained an analysis of primary photochemical processes in

Scientific Ideas of Academician N.M. Emanuel and Modern Science

11

molecular pigments and akin organic compounds. The report by R.F. Vasilyev was concerned with chemoluminescence studies. At the 5th session of the Conference, six reports were made. Prof. E.B. Burlakova in the lecture, "Bioantioxidants is a new page in pharmacology," emphasized the importance and great practical use of the studies on bioantioxidants. The next five lectures delivered at the session were devoted to liquid-phase oxidation in microheterogeneous systems (O.T. Kasaikina), theoretical and practical aspects of the chemistry of spatially hindered phenols (V.B. Volyeva, I.S. Belostotskaya, N..L. Komissarov, and G.A. Nikiforov), principles of stabilization of subcellular structures by functioning (V.N. Luzikov), mechanisms of chaperone-like activation (B.I. Kurganov), and novel molecular mechanisms responsible for ageing (A.M. Olovnikov). A wide discussion of the reports delivered was held. The Conference showed that many ideas put forward by Emanuel have found a wide application; part of his hypotheses is being developed by his followers and scientists who work in the leading research centers of many countries and continents.

In: Chemical and Biochemical Physics: New Frontiers ISBN 1-60021-165-8 Editor: G. E. Zaikov, pp. 13-27 © 2006 Nova Science Publishers, Inc.

Chapter 3

ENERGY OF CHEMICAL BOND AND SPATIAL-ENERGY PRINCIPLES OF HYBRIDIZATION OF ATOM ORBITALS G. А. Коrablev∗ and G. E. Zaikov Basic Research-educational Center of Chemical Physics and Mesoscopy, Udmurt Research Center, Ural Division, RAS, Izhevsk, Russia Institute of Biochemical Physics after N.M. Emanuel, RAS, Moscow, Russia

ABSTRACT Methods for evaluating energy directedness of atom orbital hybridization and calculating the energy of chemical bonds in simple and complex structures are proposed based on the application of spatial-energy parameter (P-parameter) concept. The appropriate calculations and comparisons for 68 compounds were made. The results of calculations are coordinated with experimental data.

Key words: spatial-energy parameter, hybridization of atom orbitals, bond energy.

INTRODUCTION The bond energy is a direct measure of chemical bond strength. Its value is determined by the work necessary to destruct the bond between the atoms of molecular structure (or the gain of energy in the formation process of this structure from atoms). If the molecule contains two or more similar bonds, the break-off energy of this bond differs from its average energy (by all bonds). The values of bond energy of electrons of free atoms are calculated by quantummechanical methods via the wave functions, for instance in [1]. But their practical application for determining the energy values of inter-atomic bonds of actual structures produces ∗

E-mail: [email protected]; [email protected]

G. А. Коrablev and G. E. Zaikov

14

significant difficulties since the values of electron bond energy in these structures depend upon the changes in electron and nucleus configuration of the systems, especially during the hybridization of atom orbitals. The prognostic evaluation of such processes is still not properly developed. Therefore the main computational method for determining the values of chemical bond energy is the use of corresponding thermal-chemical values (enthalpies of formation of reaction products and initial molecule). It is of interest both in theoretical and practical aspect to arrange a more direct dependence between the character of changes in initial energy characteristics of atom and value of chemical bond energy. In this respect it is perspective to experimentally study the electron spectra of different (not only molecular) structures by means of X-ray electron spectroscopy (XES) that allows estimating the electron bond energies in complex systems [2]. In this research the attempt is made to estimate the energy of chemical bonds based on initial spatial-energy characteristics of free atoms with the help of the concept on spatialenergy parameter (Р-parameter), taking into consideration their changes during the hybridization of atom orbitals.

METHOD SUBSTANTIATION The analysis of various physical-chemical macro- and microprocesses results in the conclusion that in many cases the inverse values of kinetic or energy parameters of subsystems are added when estimating the resulting interaction of atom-molecular structures. Therefore tabulated (initial) values of spatial-energy parameters can be calculated based on the principle of addition of inverse values of energy components of free atom systems [3]:

1

Р0

Р

E

=

1

q =

2

1

+

(1)

( wrn)i

∑ Р0 R

(2)

where: Wi – bond energy of electrons [1]; ri – orbital radius of i-orbital [4]; ni – number of electrons of the given orbital; q=Z*/n*, where Z* and n* – nucleus effective charge and effective main quantum number [5,6]; R – dimensional characteristics of atom bond. Values of Р0-parameter are constant for electrons of i-orbital of the given atom. As described in [3] РE-parameter numerically equals the energy of valence electrons in atom static model, is a direct characteristics of electron density inside the atom at the given distance from the nucleus and, therefore, can be used to estimate the kinetics of chemical reactions and chemical bond energy of structures.

Table 1. Р-parameters of atoms calculated via the bond energy of electrons Atom 1 Н

С

N

O

O

Valence electrons 2

W (eV) 3

ri (Å) 4

q2 0 (eVÅ) 5

Р0 (eVÅ) 6

R (Å) 7

Р0/R (eV) 8

1S1

13.595

0.5295

14.394

4.7985

2P1 2P2

11.792 11.792

0.596 0.596

0.5295 0.46 0.77 0.77 0.69

9.0624 10.426 7.6208 13.066 14.581

2P3г 2P1г 2S1 2S2 2S1+2P3г 2S1+2P2 2S1+2P1г 2S2+2P2 2P1 2P2 2P3 2P4г 2P5г 2S1 2S2 2S2+2P3 2P1 2P2 2P4 2S1 2S2 2S2+2P4

19.201

15.445

25.724 25.724

0.620

0.4875

0.521 0.521

35.395 35.395 5.8680 10.061

37.240

13.213 4.4044 9.0209 14.524 22.234 19.082 13.425 24.585

52.912

6.5916 11.723 15.830 19.193 21.966 53.283 53.283 10.709 17.833 33.663

17.195 17.195 0.4135 0.4135 71.383 71.383 6.4663 11.858 17.195 33.859 33.859

0.4135 0.450 0.450

71.383 20.338 72.620 72.620 12.594 21.466 41.804

0.77 0.77 0.772 0.710 0.710 0.77

11.715 18.862 28.801 26.876 34.627 31.929

0.71

9.2839

0.71 0.55 0.55 0.71 0.71 0.71 0.66 0.66 0.59 0.66 0.66 0.66 0.66 0.59

22.296 34.896 39.938 15.083 25.117 47.413 9.7979 17.967 20.048 30.815 19.082 32.524 63.339 70.854

k

РE/k

Р0/rI (eV) 12

9

10

rI (Å) 11

1

9.0624

1.36

3.528

1 2

7.6208 6.533

2.60 2.60

2.2569 3.8696

1

11.715

2.60 2.60

3.470 5.5862

4 3

7.2003 8.9587

4 4

8.657 7.982

2.60 0.20

9.456 122.9

3 3 5

5.2767 11.632 7.9876

1.48

10.696

5

9.4826

1.48

22.745

2

8.9835

1.36

8.7191

1.36

14.954

1.36

30.738

4

Table 1. Р-parameters of atoms calculated via the bond energy of electrons (Continued) 1

2

3

4

5

6

7

8

9

3P1

8.0848

1.068

29.377

6.6732

1.17 1.34 1.34 1.17 1.11 1.34 1.17 1.34 1.17 1.11 1.11

5.7036 4.990 8.1164 9.2974 12.402 10.723 8.4373 7.3669 13.428 23.952 21.295

4

1.24 1.39 1.24 1.39

5.6991 5.084l 9.7355 8.6649

3P2

10.876

3P3г

13.766

Si 3S1 3S2 3S + 3P2 3S1+3P3 4P1

14.690

0.904

38.462

9.8716

41.372

15.711 26.587 23.638 7.0669

2

Ge

F

7.8190

1.090

4P2

12.072

4Р3 4S1

15.803 10.855

15.059

0.886

58.223

4S2

18.298

4S2+4P2

30.370

4S1+4P3 2P1 2Р3 2P5 2S1 2S2 2S1+2P3 2S2+2P5

19.864

0.3595

93.625

42.792

0.396

94.641

26.658 6.6350 17.433 25.648 14.375 24.961 31.808 50.809

1.24 1.39 1.24 1.39 1.24 1.39

10

11

12

5.988 5.3238

0.39

68.172

0.65

18.572

4 4 4 4 4 4 4

8.7540 7.8094 14.756 13.164 24.492 21.849

69.023

0.64 0.64 0.64 0.64 0.64 0.64 0.64

0.44

10.367

1.33

4.9887

40.388 22.461 39.002 49.700 79.388

1.33

19.435

1.33

38.202

4

12.425

Table 1. Р-parameters of atoms calculated via the bond energy of electrons (Continued) 1

2 5P

1

3

4

5

6

7

8

7 .2124

1.240

47.714

7.5313

1.42 1.58 1.42 1.58 1.42 1.42 1.58 1.42 1.58 1.42 1.58 1.00

5.3037 4.7666 9.1613 8.2336 12.094 7.7838 6.9956 13.307 11.959 18.611 16.726

Sn 5P2 5Р3г 5S1

13.0091

12.965

1.027

65.062

5S2

Cl

Br

I

5P2+5S2 3P1 3Р3 3P5 3S1 3S2 3S1+3P3 3S2+3P5 4P1 4P3 4P5 4S1 4S2 4S1+4P3 4S2+4P5 5P1 5P3 5P5 5S1 5S2 5S2+5P5

17.173 11.053 18.896

13.780

0.7235

59.844

13.780 29.196 29.196

0.7235 0.660 0.660

59.844 79.928 79.928

12.438

0.8425

73.346

27.013

0.730

100.21

10.971

22.345

1.0215

0.876

77.651

103.44

26.427 8.5461 19.943 .27.196 15.526 1.00 1.00 26.002 35.468 1.00 53.198 1.00 9.1690 22.005 30.563 16.477 28.300 38.462 58.863

1.14 1.14

9.7936 23.462 32.548 16.459 28.400 60.948

1.35 1.35

1.14

9

8.5461

10

11

12

1.02

12.754

0.67 0.67 1.81

4.7216

8.867 1.81 1.96

29.391 4.6781

38.443

27.196 15.526 35.468 53.198

4

8.0430 26.809 14.454 24.825 33.739 51.634 7.2545 13.739 24.109 12.192 21.037 45.147

4

3

8.4348 (0.39) 2.20 4.580

150.93 4.4516

0.50

121.90

18

E.B. Burlakova and G.E. Zaikov

Р0 and РE-parameters of free atoms were calculated based on equations (1, 2), the results of which are given in Table 1. For hydrogen atom the value of Bohr radius of hydrogen atom equaled to 0.529Å and besides, for some cases – ionic radius (1.36Å) were used as the main dimensional characteristics. All atoms, covalent and ionic radii were taken basically according to Belov-Bokii. For atoms С, N and О also the possibility to change covalent radii depending upon the bond repetition factor was taken into consideration. For the same elements average statistical values of P-parameters are given as РE / k – where k – hybridization coefficient, that assumes the possibility to further calculate average value of bond energy.

SPATIAL-ENERGY PRINCIPLES OF HYBRIDIZATION Hybridization means the mixing of atom orbitals of different types of the given atom in one molecular (or atom) orbital. Hybridization principles are well-developed in accordance with the experimental data in the frames of general theories of valence bond (VB) and molecular orbitals (MO). But the sources of energy directedness of hybridization processes have to be further investigated and discussed. In [1] there is a conclusion based on the analysis of multiple computational and experimental data that the most valence-active are the orbitals with minimum values of P0parameters. Let us apply this principle to the hybridization of atom orbitals on the example of carbon and nitrogen atoms. 2

2

Carbon ( 2 s 2 p ). From Table 1 we can see that maximum value of P0-parameter of

2 p 2 -orbital equals 10.061 eVÅ, but the minimum value of P0-parameter of 2s 1 -orbital is 1

smaller (equaled to 9.029 eVÅ). This means that 2s - orbital is more valence-active than

2 p 2 -orbital. This conditions their hybridization. The calculation according to equation (1) 3

produces the value of P0-parameter of 2 p (hybridized) orbital equaled to 13.213 eVÅ. This 2

is much smaller than P0-parameter of 2s -orbital (14.524 eVÅ). Therefore, only the 3

1

2

1

1

1

following hybridization options can occur: 2 p + 2s ; 2 p + 2s ; 2 p + 2s ; this 3

2

corresponds to single, double and triple bonds of hybridization of sp , sp and sp types. 2

3

3

1

Nitrogen ( 2 s 2 p ). P0-parameter of 2 p -orbital equals 15.830 eVÅ, and 2s -orbital – 10.709 eVÅ. Therefore, they are hybridized with the formation of 2p4г-hybridized orbital responsible for σ -bond sp hybridization where Po =19.193 eVÅ. But this is still greater 2

than P0-parameter of 2s -orbitals (17.833 eVÅ). That is the hybridization process will 2

continue due to 2s -orbital with the formation of 2p5г-orbital ( Po =21.966 eVÅ) responsible for 2π-bond of s − p hybridization.

Scientific Ideas of Academician N.M. Emanuel…

19

These are main hybridization options of orbitals in carbon and nitrogen atoms in this 2

2

approach. Less possible are metastable states with the hybridization of 2s + 2 p type with 2

3

carbon and 2s + 2 p - of nitrogen. The initial hybridization principle is applied for the analysis of energy directedness of mixing of atom orbitals for some other structures (Table 2). Computational values of P0parameter of hybridized orbitals were further used to determine bond energies (Е). In the supposition of pair inter-atomic interaction the structural PC-parameter was calculated [1,7] following the principle of the addition of inverse values of initial values of Р-parameters, and in this case – based on the following equation:

1 1 1 1 = = + N Е Р С (Р E K )1 (Р E KN )2

(3)

where N – coefficient of bond repetition factor, К – hybridization coefficient that usually equals the number of registered atom valence electrons. The half of inter-nuclear distance was frequently used as a dimensional characteristics R for binary bond. The same – for hydrogen atom in halogen-hydrogen. The corresponding calculations for several structures are given in Table 2. From Table 2 it is seen that hybridization coefficient (K) in the crystalline carbon structures observed equals the coordination number. And for σ -bond of nitrogen К=3, this corresponds to the number of valence electrons 2 p -orbital: к1 = 3

n1 =3.

The comparison of computational values with experimental data by bond energy [8] given in Table 2 characterizes rather high efficiency of this method. Usually a ratio error does not exceed 0.1% and not more than 5% in other cases. Besides, it should be noted that the given model mainly confirms the approved conclusions and results of the corresponding computational methods of bond energies as applicable to certain structures, the list of which in this paper is limited only by the authors’ interests.

CALCULATION OF CHEMICAL BOND ENERGY VIA THE AVERAGE VALUES OF P0-PARAMETERS The application of methods of valence bond and molecular orbitals to complex structures meets significant difficulties regarding the prediction of hybridization energy directedness and type of bonds being formed. Let us consider several opportunities of using P0-parameter method. It is practicable to apply equation (3) to calculate the energy of chemical bonds, where К – mixing or hybridization coefficient that usually equals the number of registered valence electrons, and Рэ (N/к) has a physical sense of averaged energy of spatial-energy parameter falling on one valence electron of registered orbitals. But for complex structures

Рэ -parameter is averaged by all main valence orbitals.

20

E.B. Burlakova and G.E. Zaikov

Let us first approve such an approach on binary molecules. For binary molecules the dissociation energy (Do) corresponds to the value of chemical bond energy: Do=Е. The results of calculating the dissociation energy by equation (3) given in Table 3 showed that РС=D0. For some molecules containing F, N and О the values of ion radius (in Table 3 marked with *) were used to register the ionic character of the bond in the process of РE-parameter calculation. For molecules С2, N2, O2 the calculations were done by divisible bonds. In other cases, the average values of bond energy were calculated. Computational data are not in conflict with the experimental [8]. With similar computation of average values of bond energy in complex structures the average values of РE-parameters (taken from Table 1) were considered as well, but taking valence sub-levels into account (Table 4). In these cases РС=Е (bond energy). It is also shown that in most cases, due to the influence of all the valence electrons of atoms, it is possible as a first approximation to be limited with the estimation of interaction only between basic bond atoms (for instance, С-Н in hydrocarbon structures). To a greater extent this refers to hydrocarbon organic structures. But for nitrogen oxides and hydrides more accurate results are obtained with preliminary calculations of РС-parameters of reaction intermediate products following the equation (3). Then E is calculated according to the following equation: 1 = Е

1

+

(4)

1

РС1 РС 2

Where

РС1 and

РС2 - РC-parameters of complex structure parameters.

Calculations based on equations (3 and 4) are given in Tables 3 and 4. At the same time, in some cases the results of calculations of bond energy for fragments of NH2, NO2 and N2O that are introduced into other complex structures are given. The deviations of computational data from the experimental ones [8] do not exceed 10% for complex structures.

CONCLUSIONS 1. The energy of chemical bond in simple and complex structures can be satisfactorily determined by means of Р-parameter method based on initial spatial-energy characteristics of free atoms taking hybridization of their atom orbital into account. 2. The proposed method for estimating the energy directedness of mixing atom orbitals agrees with the experimental data.

Table 2. Computation of bond energy taking into account the hybridization of atom orbitals

Structure

1 Diamond Graphite (1)

Bond

2

3

σ с−с

σ

с−с Graphite (2)

σ с−с

Carbyne (− с ≡ с − )m Ethylene H 2 C = CH 2

Hybridization

single

sp

Orbitals

4 3

2s

1

2p3г

7 0.772

8 28.801

9 1/4

10 28.801

11 1/4

.

(N/к)1

(eV)

Pэ

(N/к)2

Рс (eV)

(eV)

calculation

experiment

12 3.600

13 347.5

14 347.3

0.710

26.876

1/3

26.876

1/3

4.479

432.4

418.7460.6

s2 p2

2s 2 2 p2

14.524 10.061

24.585

0.710

34.627

1/4

34.627

1/4

4.3283

417.8

418.7

sp

2s 1

9.0209 4.4044

13.425* * 1/2

0.6895

9.7365

1/4

9.7365

1/4

1.2170

117.5

108.9

г

sp 2

2s 1 2 p2

9.0209 10.061

19.082

0.665

28.695

2/4

28.695

2/4

3.587

346.2

347

sp

2s 1

9.0209 4.4044

13.425

0.601

22.375

3/4

22.375

3/4

8.391

807.6

782

4.4044 4.4044

8.8088

0.601

14.657

1/4

14.657

1/4

1.832

176.8

НС≡ СН

с−с

2p

π

2s 1

+π

6 22.234

( Ao )

Рэ

 kJ  Е   mol 

19.082

σ

σ

5 9.0209 13.213

R = d2

″

9.0209 10.061

Acetylene

с−с

(eV)

(eV)

о

′

2s 1 2 p2

2p

с−с

∑Р

Ро

′

sp 2

1

σ

Rk

′

1

г

2p

1

г

984.4

962.3

Table 2. Computation of bond energy taking into account the hybridization of atom orbitals (Continued) 1 Methane (1)

СН 4 Methane (2) Ethane

σ

2

C-H C-H

σ

Н 3С − СНс − с N-N

3

sp

3

2s

2p3г

σ

SiН4

6 22.234

7 0.546

8 40.722

¼

9

4 . 7985 0 . 546

10

11 1/1

12 4.716

13 455.3

435.1

14

2s 2 2 p2

14.524 10.061

24.585

0.77

31.929

¼

9.0624

1/1

4.243

409.6

410

sp 3

2s 1

9.0209 13.213

22.234

0.772

28.819

¼

28.819

¼

3.6024

347.7

345.6

6.5916 6.5916

13.183

0.71

18.658

1/3

18.658

1/3

3.095

298.7

318

11.723 11.723

23.446

0.63

37.216

1/3

37.216

1/3

6.2026

598.7

586

2p4г

19.193

19.193

0.55

34.896

1/3

34.896

1/3

5.8161

561.4

543.4

2p5г

21.966

21.966

0.55

39.938

1/5

39.938

1/5

3.9938

385.5

3s2 3p2

15.711 10.876

26.587

1.11

23.952

¼

23.952

¼

2.994

946.9 289

3p3г 3s1 3p3г

13.766 9.8716 13.766

13.766 23.638

1.34 0.738

10.273 32.030

1/3 ¼

10.273 9.0624

1/3 1/1

1.712 4.251

165.3 410.3

3

2p _

г

2 p1 2 p1

N=N

Silicon Si2 → 2Si

5 9.0209 13.213

_

Nitrogen N2

N2 N≡N

4 1

_

2 p2 2 p2

sp

N-N 2π N-N N-N σ +π Si- Si

σ

Si-Н

2

s p sp

3

2

947.6 305 ± 3 309.6 ± 13 176 395

Table 2. Computation of bond energy taking into account the hybridization of atom orbitals (Continued) 1

2

3

4

5

6

7

8

9

10

11

12

13

14

Germanium Ge2 → 2Ge

Ge-Ge

sp3

4s1 4p3г

10.855 15.803

26.658

1.22

21.851

1/4

21.851

1/4

2.7314

263.6

273 278 ± 13

4p3г

15.803

15.803

1.39

11.369

1/3

11.369

1/3

1.895

183

168

Tin Sn2 → 2Sn Sn(||) Sn(|\/ )

HF

σ

Sn- Sn

5p3г

5p3г

17.173

17.173

1.42

12.094

1/3

12.094

1/3

2.016

194.6

Sn- Sn Sn- Sn

p2

5p2 52 5s2

13.009 13.009 18.896

13.009 26.427

1.63 1.58

7.981 16.726

1/2 1/4

7.981 16.726

1/2 1/4

1.995 2.098

192.6 202.5

192.5 ± ± 16.7 192.5 192.5

2s 1

14.375 17.433

31.808

0.64

49.700

1/4

4.79851/ 0.438

1/1

5.822

562

566

15.526 19.943

35.468

1.00

35.468

1/4

4.7985/ 0.529

1/1

4.482

432.6

427.8

16.477 22.005 23.462

38.462

1.14

33.734

1/4

1/1

3.769

363.9

362.5

23.462

1.35

17.379

1/3

4.7985/ 0.704 4.7985/ 0.8045

1/1

2.94

283.7

294.6

σ F-H

HCl

σ Cl-H

HBr

σ

HI

Br-H I -H

2

s p sp 2

2

3

sp

2

sp 2 p3

2p 3s1 3p2 4s1 4p3 5p3

 kJ    mol 

Table 3. Dissociation energies of diatomic molecules – D0 

First atom Structure 1 CCl CBr CJ CN CN C-O NO CH OH ClF ClO ClО FO NF NCl H2 Li2 B2 C-C C=C N-N N=N O-O O=O *

Orbitals

N/k

РE (eV)

2 2Р1 2Р1 2Р1 2Р2 2Р2 2P2 2Р1 2Р2 2Р2 3S23P5 3S23P5 3Р1 2Р1 2P3 2P3 1S1 2S1 2Р1 2Р1 2Р2 2P3 2S22P3 2Р2 2S22P4

3 1/1 1/1 1/1 2/2 2/2 1/2 1/1 1/2 1/2 1/7 1/7 1/1 1/1 1/3 1/3 1/1 1/1 1/1 1/1 2/2 1/3 2/5 1/2 2/6

4 7.6208 7.6208 7.6208 13.066 14.581 13.066 9.2839 13.066 17.967 29.391* 29.391* 4.7216* 4.9887* 10.696* 22.296 9.0624 2.2419 5.4885 7.6208 13.066 10.696* 22.745* 8.7191 30.738*

Second atom РE N k 5 7.6208 7.6208 7.6208 13.066 14.581 6.533 9.2839 6.533 8.9835 4.1987 4.1987 4.7216 4.9887 3.5653 7.432 9.0624 2.2419 5.4885 7.6208 13.066 3.5653 9.098 4.3596 10.246

Orbitals

N/k

РE (eV)

6 3Р1 4Р1 5Р1 2S22P3 2P3 2P2 2Р2 1S1 1S1 2S22P5 2Р2 2S22P4 2Р2 2Р1 3Р1 1S1 2S1 2Р1 2Р1 2P2 2P3 2S22P3 2Р2 2S22P4

7 1/1 1/1 1/1 2/5 2/3 1/2 2/2 1/1 1/1 1/7 2/2 1/6 1/2 1/7 1/1 1/1 1/1 1/1 1/1 2/2 1/3 2/5 1/2 2/6

8 8.5461 8.0430 7.2545 47.413 25.127 17.967 20.048 9.066 9.066 38.202* 8.7191* 30.738* 8.7191* 38.202* 8.5461 9.066 2.2419 5.4885 7.6208 13.066 10.696* 22.745* 8.7191 30.738*

Calculations of РE-parameter are given using ion radius based on the equation: РE=ΣР0 / rI

РE N k 9 8.5461 8.0430 7.2545 18.965 16.751 8.984 20.048 9.066 9.066 5.4574 8.7191 5.123 4.3596 5.4574 8.5461 9.066 2.2419 5.4885 7.6208 13.066 3.5653 9.098 4.3596 10.246

РС (eV)

D0 calculation

D0 experiment

10 4.0209 3.9130 2.2523 7.7358 7.796 3.782 6.346 3.7969 4.5118 2.5579 2.8337 2.450 2.327 2.486 3.9751 4.533 1.121 2.744 3.810 6.533 1.783 4.549 2.1798 5.123

11 388.9 377.7 217.4 746.7 752.5 365 612.5 366.5 435.5 246.9 273.5 237.2 224.6 239.5 383.7 437.5 108.2 264.9 367.8 630.6 172.1 439 210.4 494.5

12 393.3 364 209.2 755.6 755.6 356 626.8 333±1 423.7 229.1 264 264 219.2 298.9 384.9 432.2 98.99 276±21 376.7 611 161 418 213.4 498.3

kJ  Table 4. Energy of bond breaking-off in complex structures – Е    mol 

No

First atom

Reactions

Bond breaking-off

orbitals

N/k

1

2

3

4

1 2 3 4 5 6

СН2=СН+Н СН3=СН2+Н СН4=СН3+Н С2Н4=С2Н3+Н С2Н6=С2Н5+Н С6Н6=С6Н5+Н

С---Н

7

СН2=СН+Н

С---Н

8 9 10 11 12 13 14 15

СН4=СН2+Н2 С2Н5=СН3+СН2 С2Н6=2СН3 С3Н8=С2Н5+СН3 О2=О+О СН3О·ОН= СН3О+ОН Н2О2=2ОН Н2О2=2ОН

16

17

2S22P2

2P2 2

1/4

1/2

Second atom РE (eV) РI 5

7.982

orbitals 6

1S1

6.533

1S1 1

Calculation

Experiment Е

N/k

РE (eV)

Е

7

8

9

1/1

9.0624

409.7

10.426

436.4

1/1

9.0624

366.5

С---(Н2)

2P

1/2

6.533

1S

2·1/1

2·9.0624

463.6

С---С

2S22P2

1/4

7.982

2S22P2

1/4

7.982

385.2

О=О -О-О-О-О(ОН)-(ОН)

2P2 2P4 2P2

2/2 1/4 1/2

17.967 14.954* 8.7192 4.5118

2P2 2P4 2P2

2/2 1/4 1/2

17.967 14.954* 8.7192 4.5118

N2=2N

N–N

2S22P3

1/5

22.745

2S22P3

1/5

22.745

N2Н2=NН+NН

N=N

2S22P3

2/5

2S22P3

2/5

8.898*

22.745

2 =8. 5 *

898

180.4 210.4 217.8 219.5 (2.275 eV) 439.1

10

430±12.6 457±12.6 >434.8 435±4.2 438.9 445.2 457.3 338.9 364 432.6 416.7±8.4 372.4 380.7 — 181.5±19 231.8±2.5 231.8±2.5

472.8±33.5

kJ  Table 4. Energy of bond breaking-off in complex structures – Е   (Continued)  mol 

No 18

1 NН2=N+Н2

19

N2Н4=2(NН2)

20 21

*

Reactions

СН3NHNH2= СН3NH+ NH2 NO2=NO+O

Bond breaking-off

First atom

Second atom РE (eV) РI 5 10.696*

orbita ls 6 1S1

РE (eV)

Е

Е

7 1/1

8 9.0624

9 (Рi-5.118 eV)

10

5.118*

247

252.7±16.7

3

1/3 1/5

10.696* 22.745*

172.1 219.5

175.7 217±4

4.4525

2P2

2/2

8.7191*

284.5

305.9

1/1

9.2839

1

2P

1/1

9.7979

460.2

481.8

— 1/5

22.745* 9.4826

— —

— —

8.7191* 8.9835

172.5 445.3

167.4 439.3

N/k

2 N=N (NН2)(NН2)

3 2P3

4 2/3

N-N N-N

2P3 2S22P3

1/3 1/5

10.696* 22.745*

(≡N=O)---O

2S22P3

—

5.118*

22

N2O=NO+N

N-O

2P

23 24

N2O=(N2)+O NO2=N+O2

(N2)=O (N)-(O2)

— 2S22P3

calculations of РE-parameter are done using the ion radius (rI)

Experiment

N/k

orbitals

1

Calculation

2P3 2S22P

Energy of Chemical Bond and Spatial-Energy Principles…

27

REFERENCES [1] [2]

[3] [4] [5] [6] [7]

[8]

Fischer C.F. Average – Energy of Configuration Hartree – Fock Results for the Atoms Helium to Radon//Atomic Data.-1972. №4. p. 301-399. Klyushnikov O.I., Salnikov V.R., Bogdanovich N.M. Investigation of pyrovakites La0.8ХSr0.2MnO3 by means of X-ray electron spectroscopy. Chemical physics and mesoscopy. 2001. v.3. №2. p. 173-185. Korablev G.A. Spatial-Energy Principles of Complex Structures Formation. Netherlands. Brill Academic Publishers and VSP. 2005. 426 p. (Monograph). Waber J.T., Cromer D.T. Orbital Radii of Atoms and Ions //J.Chem. Phys —1965.-V 42.-№ 12.-р. 4116- 4123. 5 Clementi E., Raimondi D.L. Atomic Screening constants from S.C.F. Functions. 1.// J.Chem. Phys.-1963.-v.38.-№11.-p.2686-2689. Clementi E., Raimondi D.L. Atomic Screening Constants from S.C.F. Functions. II.//J. Chem. Phys.-1967.-V.47. № 4.-p. 1300-1307. Korablev G.A., Kodolov V.I. Dependence of activation energy of chemical reactions upon spatial-energy characteristics of atoms – Chemical physics and mesoscopy. UdRC RAS. Izhevsk. 2001. №2.v.3. p.243-254. Gurvich L.V., Karachentsev G.V., Kondratjev V.I. et al. Breaking-off energies of chemical bonds. Ionization potentials and affinity with an electron. M: Science. 1974. 351 p.

In: Chemical and Biochemical Physics: New Frontiers ISBN 1-60021-165-8 Editor: G. E. Zaikov, pp. 29-40 © 2006 Nova Science Publishers, Inc.

Chapter 4

PREPARATION AND APPLICATION OF MAGNETIC ADSORBENTS IN BIOLOGICAL AND MEDICAL INVESTIGATIONS E. K. Dobrinskiy 1, S. I. Malashin 1, V. G. Gerlivanov 1, G. V. Stepanov 1∗, V. I. Filippov 2, L. Kh. Komissarova 2, L. A. Goncharov 2, F. S. Bayburtskiy 2†, T. V. Tsyganova 2 and H. U. Lubman 2 1

Research Institute of Chemistry and Technology of Hetero-organic Compounds, Moscow, Russia 2 N. M. Emanuel Institute of Biochemical Physics, Russian Academy of Science, Moscow, Russia

ABSTRACT The plasmachemical technology of iron–carbon adsorbent production was developed and optimized. The adsorbent was thoroughly studied by physical, chemical and biological methods, and was found to have high sorption capacity, long desorption time, high magnetization and low toxicity. The adsorbent is intended to be used for magnetically guided transport and forming a depot of anti-cancer drugs in the tumor zone.

Keywords: Magnetic adsorbent; plasmachemical technology; activated charcoal; adsorption; toxicity; magnetically guided transport of drugs; oncology.

∗

†

E – mail: [email protected], [email protected] E – mail: [email protected], [email protected]

30

E. K. Dobrinskiy, S. I. Malashin, V. G. Gerlivanov et al.

INTRODUCTION At the First International Conference on Scientific and Clinical Applications of Magnetic Carriers (1996) we described the clinical applications of magnetic adsorbent particles [1], including detoxification of biological fluids [2], concentrating of pathogens for diagnostic purposes [3], protection of implants [4] and magnetically controlled transport of anti-cancer drugs [1]. Oncological applications of the adsorbents [1,5,6] are aimed at solving the problem of localizing a highly toxic cytostatic drug in the tumor and thus reducing the general toxic effect of chemotherapy on the organism. This is accomplished in several steps. The drug is first adsorbed on the particles, a suspension of which is injected through a catheter into a regional artery feeding the tumor. An external magnetic field (generated by a source outside the organism), superimposed onto the tumor zone, causes the particles to aggregate and presses the formed clusters against the blood vessel walls. The aggregates are retained in the tumor both by the field and by getting stuck in capillaries inside the tumor. Such «microembolization» reduces the blood supply to the tumor. The drug is slowly released from the particles over a period of time, creating a high local concentration of the drug in the tumor tissue, while minimizing the amount of the drug throughout the rest of the patient’s body. Since the late 1980s this method has passed a full cycle of animal studies and clinical trials in Russia’s clinics, including more than 150 patients with the advanced stages of the disease. Majority of the patients have shown improvement in their condition, some made full recoveries [1,6]. The targeted drug delivery using magnetic particles and external magnetic field imposes several requirements on the adsorbent particles. The particles themselves must be biologically inert and biodegradable. They must also have high sorption capacity for the drug and the rate of the drug desorption in an organism needs to be slow, so that the high concentration of the cytostatic drug can be maintained in the tumor area for a prolonged period of time. Since the particles must be effectively controlled by the applied magnetic field, both their magnetic properties and their dispersity and agglomeration degree are important. High magnetic susceptibility and high saturation magnetization allow the particles to be effectively controlled by a relatively weak field and rapidly aggregate in it. Low coercive force will prevent aggregation of the particles prior to superimposition of the field. Size is also a crucial factor: very small particles (less than 0.1 lm in diameter) have a small magnetic moment and a relatively large surface. This makes it difficult to overcome hydrodynamic forces (e.g., in the bloodstream) for these particles with currently feasible magnetic forces. On the other hand, it is difficult to form stable suspensions of dense particles larger than 2 µm, and it difficult to inject suspensions of such particles through a catheter. The adsorbent also should not contain a free-flowing non-ferromagnetic fraction because it could carry the drug but would not be controlled by the magnetic field and thus can migrate to other organs. The Cefesorb-type particles (produced by joint reduction of carbon monoxide CO and iron oxides FeXOY), which were used in our earlier studies [1 – 6], generally meet the above criteria. However, their sorption capacity is relatively low (less than 27 µg/mg) and characteristics of this type of particles are not very stable (small variations in manufacturing conditions lead to rather significant changes in the product properties, thus properties of differente batches can very widely.

Preparation and Application of Magnetic Adsorbents…

31

The magnetic particles can also be produced by two other methods: (1) long-term joint grinding of iron and carbon powders [1, 7] and (2) plasmachemical re-condensation of iron and carbon [1,8]. The main drawback of the first method is that it produces a significant nonferromagnetic fraction, which is not controlled by the field and can be carried (along with a highly toxic drug) by the bloodstream to other (healthy) organs. The plasmachemical method typically produces dense particles with a small specific surface and, therefore, low adsorption capacity. In this paper, we describe a new method of production of highly efficient magnetic adsorbents using plasmachemical technology.

PLASMACHEMICAL TECHNOLOGY The magnetic adsorbents were produced using direct current arc plasmathrones (Figure 1). Particles of pure iron and of activated carbon (10–20 lm diameter) were injected into the plasmathrone chamber through an opening in the electrode with the flow of argon (Ar) as a carrier gas. The gas stream brought the particles into the high temperature (6000°C) zone of the argon, where they were evaporated. Up to 20% of the arc’s energy was estimated to be used for evaporation of the particles. As soon as the vapors reached the condensation chamber, they were rapidly cooled by cyclonic flows of arc. These conditions led to the formation of finely dispersed particles. Varying the evaporation / cooling parameters and the composition of the initial mixture allows to create a wide variety of particles with different properties.

Figure 1. Sketch of the plasmathrone chamber used for preparation of adsorbents.

Significant research and engineering efforts aimed at the optimization of the process parameters resulted in the development of the plasmachemical technology for manufacturing a highly efficient magnetic adsorbent «FerroCarbon-4» (FC-4), as well as other FCadsorbents. It was found, that the key requirement for producing highly efficient magnetically guided adsorbents is to achieve the regime, in which iron particles are fully evaporated, while activated carbon particles are only partially disintegrated and sublimated, thus conserving

32

E. K. Dobrinskiy, S. I. Malashin, V. G. Gerlivanov et al.

their porous structure with a large specific surface. During rapid cooling in the condensation zone, iron re-condenses on the remaining particles of activated carbon, probably as a film initially. However, the temperature at this point is high enough for the liquid iron to form droplets due to surface tension (σFe metall = 1.8 N / m [9]). The droplets attach to the carbon structures, hence a magnetically guided adsorbent with a large specific surface is formed. The carbon vapor partially condenses on the existing particles, and the rest of it forms dense or filamentous structures.

Physical Properties of the Adsorbent The FC-4 powder was studied using a Philips Scann scanning electron microscope (Figure 2). Low magnification (Figure 2A) shows porous clusters of particles, consisting of spherical iron particles (majority <1 µm in diameter, but some are several times bigger), and odd-shaped carbon particles (several lm in size, Figure 2B,C). The nature of the bond between iron and carbon particles remains unclear.

Figure 2. Scanning electron micrographs of Ferro-carbon-4 at 40×(A) and 2000×(B, C) magnification.

Preparation and Application of Magnetic Adsorbents…

33

Transitional electron microscopy (TEM) (JEM- 100B, JEOL) of the ultrasound-treated adsorbent suspension in 0.5 % albumin solution at low magnification shows stable aggregates (which survived sonication) and separate small spherical iron particles (Figure 3, inset). The size distribution of the particles and aggregates was measured by image analysis software (Figure 3). Three fractions can be distinguished: (1) particles with a cross-section of less than 0.1 µm2 (apparently, mostly iron microspheres); (2) a majority of the particles with a crosssection of about 1 µm2; (3) a small number of particles with the cross-section of around 4 µm2. The analysis indicated that more than 90 % of the particles have a diameter between 0.8 and 1.7 µm, with an average size of 1.2 µm. This correlates well with the photon correlation spectroscopy data (PhotoCor Complex) for the suspensions, which yielded an average particle diameter of 0.6 µm. The difference can be attributed to the complex shape of the particles, which precludes accurate measurements by the photon correlation spectroscopy. Higher magnification TEM pictures enabled us to study the structure of the particles. Figure 4 A, B show that the adsorbent particle is a composite of porous carbon (dark gray) and spherical iron microspheres (black, 0.01–1 lm diameter). Some particles are linked by long thin filaments (Figure 4B), which have the structure of carbon nanotubes called tubulenes (Figure 4C). X-ray spectroscopy (DRON-3, cadmium cathode) showed the presence of different forms of iron (a-Fe, b-Fe), amorphous carbon, possibly iron carbide and dense forms of carbon, as well as Fe2O3 (Figure 5). The spectrum shows signals which are characteristic for Fe–C bonds and for a hexagonal symmetry of carbon. Small angle measurements also indicated the presence of amorphous iron. The presence of amorphous iron and iron carbide may explain the low oxidation of the adsorbent particles in water.

Figure 3. Inset: Transition electron micrograph (TEM) of FC-4 particles after ultrasonic treatment, × 8 000. Normalized distribution of particles by the area of their cross-section.

34

E. K. Dobrinskiy, S. I. Malashin, V. G. Gerlivanov et al.

Magnetic properties of ferro-carbon adsorbents were studied using a Faraday balance (Bruker). Magnetization curves in a 0 - 5 kOe field were measured for 1 µg samples of the powder. The analysis of the curves allows us to determine the saturation magnetization and the coercive force, and also to predict the behavior of the particles in different fields. All studied ferro-carbon adsorbents (Figure 6, Table 1) practically reached saturation in the 5 kOe field, and showed almost linear dependence between magnetization and the field in the work range of the field (about 1 kOe). The coercive force did not exceed 250 Oe for all adsorbents except for FC-5, which was produced on a different plasmathrone and had smaller particles. The magnetic properties of FC-4 are very similar to those of Cefesorb, which has a comparable iron content.

Figure 4. Transition electron micrograph (TEM) of FC-4 particles. (A)Structure of FC-4 particles, × 76 000, bar 0.1 µm. (B) Adsorbent particles with carbon filaments, (B)× 91 000, bar 0.1 µm. (C) Structure of a carbon filament, × 700 000, bar 0.01 µm.

Preparation and Application of Magnetic Adsorbents…

35

Figure 5. X-ray spectrum of FC-4.

Figure 6. Magnetization curve of FC-4.

Table 1. Magnetic and adsorption of ferro-carbon particles Type of particles

Iron (Fe) Сontent (%)

Magnetization (emu / g) in 5 kOe

Coercive force (Oe)

Specific surface (m 2 / g)

Sorption capacity for doxorubicin (µg / mg)

Cefesorb FC-1 FC-2 FC-3 FC-4 FC-5

40 90 72 60 44 77

43 – 82 76 50 43

300 – 150 150 250 500

100 – 60 90 146 68

27 33 64 64 66 62

Magnetic heterogeneity of FC-4 was studied by magnetic separation both in gas and in liquid. Gas phase separation was done in a small cyclone-type separator, where the agglomerates were destroyed by the turbulent flow. More than 97 % of the powder was

36

E. K. Dobrinskiy, S. I. Malashin, V. G. Gerlivanov et al.

captured by a small permanent magnet installed on the wall of the separator. Liquid-phase magnetic separation was done with a suspension of the adsorbent in a 0.5 % solution of albumin in water, treated with ultrasound. A stable hydrosol was formed. The majority of agglomerates were destroyed by ultrasound, and all non-magnetic and weak magnetic particles were released. A vial with the hydrosol was placed in a non-uniform magnetic field, and its opacity was measured using a spectrophotometer. Several minutes later, the opacity of the vial was practically identical to that of the pure albumin solution. The data thus indicate that there is no more than 3 % of a non-(ferro)magnetic phase in FC-4. Adsorption properties of the ferro-carbon particles were studied by sorption of doxorubicin hydrochloride and methylene blue (as a model system) from aqueous solutions. Concentrations of the drug and the dye were measured by spectrophotometry (Specord UV, Karl Zeiss Jena, GDR) (Figure 7A). Solutions with different concentrations of methylene blue (10–200 µg/ml) were mixed with 1 mg of FC-4 powder per 1 ml of the solution. The mixture was treated by 22 kHz ultrasound (60 W/cm2) for 2 min (on ice) and incubated for 2.5 h on a shaker at room temperature. The vials with the suspension were then placed in a 2 kOe field, which caused sedimentation of FC particles. The supernatant was measured on the spectrophotometer at 680 nm. The results were summarized in the adsorption isotherm (Figure 7B). It shows that adsorption reaches saturation at about 50 µg of the dye per ml (with 1 mg of adsorbent per ml). Kinetics of doxorubicin adsorption was measured for the 100 µg/ml solution of the drug, mixed with 1 mg/ml of FC-4. After 2 min of sonication, the suspension was incubated on a shaker at room temperature. Samples were taken after 15, 30, 45, 60, 90 and 150 min. The adsorbent particles were removed by magnetic sedimentation and the optical density of the supernatant was measured at 498 nm. The concentration of the adsorbed drug was calculated. The adsorption kinetics was fast (Figure 7C), with sorption reaching saturation after less than 1 h. The adsorption capacity of FC-4 for doxorubicin is higher than that of Cefesorb. It was discovered that the sorption capacity of the ferro-carbon adsorbents for the antibiotic drug does not correlate with the specific surface of the powder, as measured by inertial gas (Ar) adsorption (see Table 1). Apparently, adsorption of complex organic molecules depends on the size, structure, and physical and chemical properties of pores in the adsorbent, not only on the specific surface. The drug desorption kinetics is extremely important for application of the adsorbents as anti-cancer drug carriers. One milligram per milliliter of FC-4 particles were mixed with 100 µg/ml solution of doxorubicin, sonicated for 2 min and incubated on a shaker for 2.5 h. The particles were then sedimented in a centrifuge, the supernatant was removed, and the pellet of FC-4 loaded with doxorubicin was re-suspended in human blood serum at the same concentration as that of the initial doxorubicin solution. The mixture was incubated on a shaker at 37°C. Samples were taken at 6 h intervals for the first 3 days and daily thereafter, the adsorbent particles were removed by magnetic sedimentation and the optical density of the supernatant was measured at 296 nm. The concentration of the drug in solution was calculated. The desorption kinetics was slow (Figure 7D), and had two phases. Approximately 25 % of doxorubicin was released during the first 24 h and the remaining drug was released during the next 14 –15 days.

Preparation and Application of Magnetic Adsorbents…

37

Figure 7. Adsorption properties of ferro-carbon particles. (A) Absorption spectra of supernatant fluid after mixing methylene blue solution with the adsorbents and magnetic sedimentation of them. FC-2,3,4 adsorb methylene blue more efficiently, than Cefesorb. (B) Adsorption isotherm of methylene blue on FC-4. (C) Kinetics of doxorubicin sorption on FC-4. The adsorption process is rapid, and it takes about 1 h to reach saturation. (D) Kinetics of doxorubicin desorption from FC-4. The drug is slowly released in about 14–15 days.

PREPARATION OF THE INJECTED FORM OF THE MAGNETICALLY GUIDED ANTIBIOTIC Based on the above information on the adsorption properties of FC-4, the following procedure was used for preparation of the magnetically guided form of antibiotic for animal studies and is suggested for future clinical studies. One milligram per milliliter of FC-4 was mixed with water and treated with ultrasound (22 kHz, 60 W/cm2) for 2 min. Hundred microgram per milliliter of doxorubicin was added to the hydrosol, followed by 1 h incubation on a shaker at room temperature. The suspension was centrifuged at 2500 RPM for 20 min, the supernatant removed and its absorption measured at 498 nm for the determination of the drug amount adsorbed on FC-4. The pellet was re-suspended in a physiological solution with 10 µg/ml of albumin, which stabilized the hydrosol. The final hydrosol was stable (did not sediment for more than 4 h) and easily passed through a thin injection needle.

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E. K. Dobrinskiy, S. I. Malashin, V. G. Gerlivanov et al.

Toxicity Studies Toxicity and endurance doses were measured for the ferro-carbon adsorbent FC-4 (FC) and for FC-4 with adsorbed doxorubicin (FC + DR). The experiments were done with 18 – 20 g male mice of the BALB/c line. One hundred and twenty animals were used in the study. The preparation was administered by a single intravenous injection of 0.2 ml of the suspensions with different concentrations of FC or FC + DR in physiological saline solution containing 0.5% albumin (Table 2). Each concentration was tested on 6 animals. Control groups of the same number of animals received injections of the solvent in the same concentrations. Toxic doses were calculated using the technique by Miller and Tainter [10]. The error S(LD50) of LD50 measurement was calculated using the equation: S(LD50) = (LD84 – LD16)(2n) – 1 / 2, where n is the total number of animals in all test groups, which were injected with the preparation. The toxic doses are shown in Table 2. All animals died after an intravenous injection of 1 g / kg of pure FC-4. LD50 ( ±S (LD50)) of FC-4 is 692 ± 44 mg / kg. The endurance dose (the maximal dose that did not cause death of the animals) is close to the LD10 (500 mg / kg). The animals died within a week after the intravenous injection. If the dose exceeded 1 g / kg, death occurred immediately, apparently due to cardiac arrest and suppression of breathing caused by thrombosis of the lung’s vascular system. Lungs and other internal organs of these animals were found to be black presumably due to accumulation of the particles. In preliminary experiments, animals which were injected with the suspensions into the abdominal cavity survived much higher doses of FC-4, up to 20 g / kg. Death occurred only after injections of 25 g / kg into the cavity. This demonstrates, that the FC-4 itself is of low toxicity. Intravenous injections of the FC + DR complexes killed all animals at the dose of 70 mg of doxorubicin (adsorbed on FC) per kg of the animal weight. LD50 was measured to be 50 ± 2 mg / kg (by antibiotic). The maximal endurance dose (all animals survive) was estimated to be 40 mg / kg. LD50 for doxorubicin solution (without any adsorbent) is 6 mg / kg. Thus, FC + DR complexes have almost ten times lower acute toxicity, compared to a solution with the same concentration of doxorubicin. No magnetic focusing was used in these experiments. Application of magnetic focusing will create a high local concentration of the drug in the targeted area, while further reducing the toxic load on the rest of the organism [1,6]. Table 2. Toxic doses [± S(LD50)] (mg / kg) of ferro-carbon adsorbent FC-4 (FC) and ferro-carbon + doxorubicin complexes (FC + DR) for a single intravenous injection into mice of the BALB / c line Toxicity level LD100 LD84 LD50 LD16 LD10

FC 1000 871 692 ± 44 562 525

FC + DR 70 60.3 50 ± 2 44.7 41.7

Preparation and Application of Magnetic Adsorbents…

39

SUMMARY A new ferro-carbon carrier of drugs (FerroCarbon FC-4) was created. The adsorbent is designed for magnetically guided transport and creation of a depot of anti-cancer antibiotic (doxorubicin) in the tumor zone. The properties of the carrier are summarized in Table 3. The adsorbent particles are of low toxicity. Antibiotic adsorbed on FC-4 is 10 times less toxic than a solution with the same concentration of the drug. The drug is adsorbed fast, while desorption kinetics is slow. The adsorbent has good magnetic properties and optimal particle size. FC-4 thus meets the requirements for an efficient magnetically controlled drug carrier. The processes of the ferro-carbon particles formation in plasma were studied. The semiindustrial technology was optimized for full evaporation of iron particles and only partial evaporation of activated carbon particles. Rapid cooling of such mixture leads to the formation of the adsorbent with the desired parameters. Ferro-carbon adsorbents formation in plasma can be modified easily to create optimal adsorbents for other substances such as other antibiotics, toxins and pathogens. These particles can be used to solve other medical problems such as detoxification of biological fluids, protection of implants, concentrating pathogens for diagnostic purposes, and targeted drug delivery. Table 3. Physical and chemical properties of the ferro-carbon adsorbent FC-4

Adsorption capacity for doxorubicin Time of saturation of doxorubicin sorption Time of doxorubicin desorption in blood plasma Magnetization in the 5 kOe field Magnetic heterogeneity Particle size in albumine-stabilized hydrosol Time of the hydrosol (10% of FC-4) stability Composition Powder density Specific surface Acute toxicity (LD50) Pure FC-4 FC-4 + doxorubicin

66 µg / mg 1h 10 to 15 days 50 emu / g < 3 % of particles are non-magnetic 0.01 to 5 µm; average: 1.2 µm >4h 44 % α - Fe, 55 %, amorphous C, < 1 % other 0.46 g / cm2 146 m2 / g 692 mg / kg 50 mg / kg

ACKNOWLEDGEMENTS Supported in part by the grant «Developing of new methods of diagnostics and treatment of oncological diseases» from the Moscow city government.

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REFERENCES [1]

Filippov V. I., Harutyunyuan A.R., Dobrinsky E. K., in: Hafeli U., Schutt W., Teller J., Zborowski M. (Editors), Scientific and Clinical Applications of Magnetic Carriers, Plenum Press, New - York, 1996, p. 379. [2] Kutushov M.V., Filippov V.I., Dobrinsky E. K., Komissarova L. Kh. in: Hafeli U., Schutt W., Teller J., Zborowski M. (Editors), Scientific and Clinical Applications of Magnetic Carriers, Plenum Press, New - York, 1996, p. 391. [3] Vladimirsky M. A., Filippov V. I., Malashin S. I. in: Hafeli U., Schutt W., Teller J., Zborowski M. (Editors), Scientific and Clinical Applications of Magnetic Carriers, Plenum Press, New - York, 1996, p. 353. [4] Makhmudov S.Ya., Komissarova L. Kh., Filippov V. I., in: Hafeli U., Schutt W., Teller J., Zborowski M. (Editors), Scientific and Clinical Applications of Magnetic Carriers, Plenum Press, New -York, 1996, p. 495. [5] Holodov L. E., Volkonsky V. A., Komissarova L. Kh., Filippov V. I. USSR patent No 1722256, claim SU 4767768 (1989). Europatent No 90917517.6 (1990). US patent application No 730837. [6] Komissarova L. Kh., Filippov V. I., Holodov L. E., Kolesnik N. F., Proc. 6th Int. Conf. Magnetic Fluids, Paris, 1992, p. 474. [7] Allen L. M., Kent T., Wolfe C., in: Hafeli U., Schutt W., Teller J., Zborowski M. (Editors), Scientific and Clinical Applications of Magnetic Carriers, Plenum Press, New - York, 1996, p. 481. [8] Dobrinsky E. K., Malashin S. I., Gerlivanov V. G., USSR patent No 221368 (1985). [9] Weast R.C. (Editors), Handbook of Chemistry and Physics, CRC Press, Boca Raton, FL, 1987, F-22. [10] Kudrin A. N., Ponomareva G. T., Mathematics Application in Experimental and Clinical Medicine, Medicina, Moscow, 1967.

In: Chemical and Biochemical Physics: New Frontiers ISBN 1-60021-165-8 Editor: G. E. Zaikov, pp. 41-46 © 2006 Nova Science Publishers, Inc.

Chapter 5

THE MAGNETIC SORBENTS USED FOR DETOXIFICATION OF BLOOD N. P. Glukhoedov1, M. V. Kutushov 1, M. A. Pluzan 1, G. V. Stepanov 1∗, L. Kh. Komissarova 2, V. I. Filippov 2, L. A. Goncharov 2, F. S. Bayburtskiy 2† 1

Research Institute of Chemistry and Technology of Hetero-organic Compounds, Russian Federation, Moscow, Russia 2 N. M. Emanuel Institute of Biochemical Physics, Russian Academy of Science, Russian Federation, Moscow, Russia

ABSTRACT In given article use of magnetic sorbents for detoxification of blood has been investigated. Restored-iron, iron-carbon and iron-silica do not cause changes in erythrocyte's osmotic resistance and possess high sorption efficiency for substances of different molecular mass. These magnetic carriers can be recommended for extracorporeal blood detoxification of low (barbiturates), middle (bilirubin) and high (heme proteins) molecular weight substances.

Keywords: Absorptive capacity; sorption efficiency; erythrocyte; toxicity test (osmotic); heme protein; restored-iron; iron-silica; iron-carbon; surface modification; blood detoxification; barbiturates; bilirubin; blood purification.

∗

†

E – mail: [email protected], [email protected] E – mail: [email protected], [email protected]

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INTRODUCTION Magnetic carriers (MC) can be used in biochemistry and biotechnology for cell separation, immobilization of enzymes and other biologically active compounds [1,2]. The use of MC is particularly important for extracorporeal blood purification [3 – 5]. MC used for extracorporeal blood purification require a high absorptive capacity, should be selective for eliminated substances, should be hemocompatible and should have a high magnetic susceptibility so that they can be separated using a magnetic field intensity of not more than 1 T [5]. MC of iron-carbon and restored-iron types meet many of these demands but they are not hemocompatible. The encapsulation of magnetic particles is not favored as it is known [6] that the encapsulation of coal adsorbents with biocompatible polymers reduce the absorption of low molecular weight substances (MW<300 Da) and practically excluded the sorption of middle (MW 300 – 10 000 Da) and high molecular weight substances (MW > 10,000 Da). Polystyrene microspheres usually used for the absorption of proteins or for covalent coupling of ligands are not intended for the sorption of low and middle molecular substances [7]. Our aim was to find a hemocompatible coating for magnetic particles, which on one hand did not reduce the sorption capacity of low and middle molecular substances, and which on the other hand promoted the adsorption of high molecular substances. We investigated different magnetic carriers consisting of iron-silica composites, iron-carbon, but also restorediron, which is a highly dispersed powder of metallic iron containing less than 10 % of iron oxides.

MATERIALS AND METHODS MC of different types (restored-iron, iron-carbon and iron-silica) were all obtained using the same technology [8]. First, highly dispersed particles of restored-iron were fractionated at defined intervals of gas flow speeds (0.02 – 1.00 m / s) and a defined intensity of magnetic fields (10 – 10 3 A/m) in order to get fractions of particles sized 0.2 – 2 µm. The following thermal process was then carried out at 800 – 1000°C in a flow of inert gas, which contained either coal microparticles or silicon oxides. The composition of the studied MC is shown in Table 1. Their magnetic properties were studied with Faraday's magnetometer (Bruker) [5]. Measurements of the magnetic moment were performed at 20°C in a magnetizing field changing from 0 to 10 kOe. The analysis of the magnetization curves allowed the determination of the saturation magnetization (ISAT ) and made it possible to obtain the data necessary to predict the behavior of the particles in various fields. The magnetization of the particles reached saturation in a magnetic field of 1 – 2 kOe. The saturation magnetization for different types of MC are also given in Table 1. The particles with 90 % iron had an ISAT of up to 180 emu / g. Different types of MC (iron-carbon, iron-silica, restored-iron) had ISAT between 50 and 180 emu / g. The surface of restored-iron and iron-carbon particles was covered by human albumin or gelatin using Widder's method [9] in our modification [8,10]. The magnetic carrier's surface was coated with albumin or gelatin by mixing a suspension of MC and albumin or gelatin using ultrasound. The suspensions were then heated to 120°C followed by cooling to room

The Magnetic Sorbents Used for Detoxification of Blood

43

temperature (for albumin) and washing with water (for albumin and for gelatin). Surfacemodified particles were kept at 10 % concentration in distilled water at 2 – 4°C. Hemoglobin obtained from donor blood was used as high molecular weight substance. The heme proteins myoglobin, hemoglobin, methemoglobin and carboxyhemoglobin were received from the blood taken from patients with crush-syndrome, hemolysis and carbon oxide poisoning. Cyanocobalamin (Russia) and bilirubin (Lachema, Czech Rep.) were used as middle molecular weight substances. The barbiturates sodium thiopental, sodium hexenal and sodium phenobarbital were used as low molecular weight substances. Human albumin (Sigma, Germany) and gelatin (Russia) were used to coat the MC. The sorption efficiency of MC was determined as the ratio of the quantity of the adsorbed substance to its initial amount (w / w), expressed in % for a certain ratio (w / w) of adsorbent to substance. Optimal ratios of adsorbent to substance equal 15 – 20 for barbiturates, 20 – 25 for cyanocobalamin and bilirubin, and 40 – 50 for hemoglobin. The initial concentration of absorbed substances was 100 – 200 µg/ml. The substances were incubated for 1min with MC either in physiological solution or in donor plasma and donor blood at room temperature (pH 7.4). The concentration of substances in the solutions was measured by differential visual and UV-spectroscopy. Concentrations of substances in blood and plasma and adsorption of total plasma proteins was determined by thin-layer chromatography with a fluorescent label. Osmotic resistance of erythrocytes was studied by the method of HCl-hemolysis [10]. Table 1. Properties of the studied magnetic carriers (MC) Contents of MC (%) Type

Restored-iron Fe-coal Fe-silica

Metallic iron

Iron oxides

Coal

Silica

> 90 10 – 70 80 – 88

< 10 < 10 < 10

0 20 – 80 0

0 0 2 – 10

Saturation magnetization (emu / g)

175 – 180 50 – 120 140 – 150

RESULTS AND DISCUSSION More than 50 patterns of different types of MC were studied. The results of sorption efficiency of the best patterns of MC to different molecular mass substances are represented in Tables 2 – 6. The sorption efficiency of MC for different barbiturates was identical, and the results shown are thus only for sodium phenobarbital. The highest sorption of 85.7 % for phenobarbital in physiological solution was reached by the ironsilica composite (see Table 2). It was also most effective for cyanocobalamin at 33.9 %. The modification of iron-carbon particles by gelatin did not change their sorption efficiency for phenobarbital and cyanocobalamin. The maximum sorption efficiency values of hemoglobin (more than 50 %) was reached by restored-iron, followed by iron-carbon modified with gelatin, and then the unmodified MC (less than 40 %). Table 3 demonstrates that iron-carbon composite, modified by gelatin or albumin absorbs large amounts of phenobarbital and hemoglobin in donor plasma. The sorption efficiency results of MC to bilirubin in physiological solution and plasma are interesting. Table 4 shows that iron-carbon composites modified by gelatin or albumin have higher sorption efficiencies for bilirubin than unmodified particles. Also,

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albumin coated MC have a higher sorption efficiency for bilirubin in plasma than particles coated with gelatin (59.7 % versus 39.3 %, respectively). Table 5 shows that the sorption efficiency of gelatin-modified restored-iron for heme proteins (myoglobin, hemoglobin and carboxyhemoglobin) in donor blood is rather high (52 – 84 %) and it is lower for methemoglobin (22 %). The initial concentration of myoglobin does not seem to influence the sorption efficiency of MC. Table 2. Sorption efficiency of magnetic carriers (MC) for substances of different molecular mass in physiological solution at pH 7.4 Sorption efficiency, average ± SD (%) Phenobarbital MW 232 GelatinUnmodified modified

Type

Restored-iron Fe-carbon Fe-silica

38.3 ± 6.3 49.9 ± 6.8 85.7 ± 10.2

40.4 ± 7.4 55.2 ± 7.0

Cyancobalamin MW 1355 GelatinUnmodified modified

9.0 ± 6.1 21.4 ± 5.3 33.9 ± 7.7

Human hemoglobin MW 64.000 GelatinUnmodified modified

11,1 ± 3.4 23.2 ± 6.1

32.3 ± 7.1 37.6 ± 7.6 22.5 ± 5.8

54.4 ± 8.2 52.7 ± 7.8

Table 3. Sorption efficiency of magnetic carriers (MC) in donor plasma at pH 7.4 Sorption efficiency, average ± SD (%) Type

Fe-carbon Fe-silica

Phenobarbital MW 232 AlbuminUnmodified modified 46.8 ± 7.9 43.1 ± 7.2 67.3 ± 8.4

Cyancobalamin MW 1355 AlbuminUnmodified modified 13.5 ± 4.1 15.7 ± 5.8 23.1 ± 4.3

Human hemoglobin MW 64.000 AlbuminUnmodified modified 39.4 ± 7.0 44.5 ± 6.6 11.9 ± 3.8

Table 4. Sorption efficiency of magnetic carriers (type Fe-carbon) for bilirubin (MW 584) Medium of incubation (pH 7.4)

Physiological solution Donor plasma

Sorption efficiency, average ± SD (%) Without modification

Gelatinmodified

Albuminmodified

29.0 ± 5.7 0

66.7 ± 7.4 34.3 ± 5.9

70.8 ± 8.6 59.2 ± 8.1

Changes in the erythrocytes' osmotic resistance were not observed. Adsorption of total plasma proteins on modified MC was lower than 12 %, but it was about 60 – 70 % on unmodified particles. Table 6 summarizes the results obtained of MC sorption efficiency to substances of different molecular mass in donor plasma. The sorption mechanism of low and middle molecular weight substances (phenobarbital and cyanocobalamin) on iron-carbon and restored-iron MC is apparently connected with absorption of molecules into the sorbent's pores. Iron-carbon composites have a more porous structure than restored-iron, therefore the

The Magnetic Sorbents Used for Detoxification of Blood

45

sorption efficiency of iron-carbon MC is higher than that of restored-iron (see Table 2). The results show that the modification of the particle surface with gelatin or albumin does not interfere with this process. The high sorption efficiency of the iron-silica composite for phenobarbital is caused by the interaction of silica OH-groups with the barbiturate's molecules. High sorption efficiency of iron-carbon composite modified by albumin or gelatin to bilirubin in physiological solution (see Table 4) is probably connected to the formation of hydrogen bonds of bilirubin methyl-groups with carboxy-groups of albumin or gelatin [6]. Adsorption mechanism of hemoglobin and other heme proteins on the surface of MC modified by gelatin or albumin at pH 7.4 (see Table 5) can be explained by an electrostatic interaction of gelatin or albumin carboxy-groups with amino-groups of the heme proteins [10]. Such electrostatic interactions are due to the differences in isoelectric points of heme proteins on one hand, and albumin or gelatin on the other. Table 5. Sorption efficiency for heme proteins of 2 mg of the gelatin-modified restored-iron MC in 10 ml of donor blood Heme proteins

Myoglobin (ng / l) Hemoglobin (µg / l) Methemoglobin (%) Carboxyhemoglobin (%)

Concentration, average ± SD (%) Befor After 1000 ± 62.3 300 ± 22.0 640 ± 16.7 240 ± 19,8 280 ± 19.0 45.7 ± 4.1 40.6 ± 4.5 12.7 ± 1.30 27.5 ± 3.1 21.3 ± 0.9 17.0 ± 3.9 8.0 ± 0.7

Sorption (%) 70 62.5 83.8 60.7 22.5 52.9

Table 6. Sorption efficiency of magnetic carriers (MC) for substances of different molecular mass in donor plasma at pH 7.4 Sorption efficiency, average ± SD (%) Substances Fe-silica Phenobarbital Cyancobalamin Bilirubin Human hemoglobin

67.3 ± 8.4 23.1 ± 4.3 < 42 11.9 ± 3.8

Fe-carbon modified with gelatin 46.8 ± 7.9 13.5 ± 4.1 34.3 ± 5.9 39.4 ± 7.0

Fe-carbon modified with albumin 43.1 ± 7.2 15.7 ± 5.8 59.2 ± 10.3 44.5 ± 6.6

SUMMARY The novel magnetic carriers of an iron-silica type iron-carbon or restored-iron composites modified by gelatin as well as the albumin do not cause changes in erythrocytes' osmotic resistance and no noticeable adsorption of total plasma proteins. The magnetic carriers have good magnetic characteristics and a high sorption efficiency for substances of different molecular mass. They can be recommended for extracorporeal blood detoxification for low (barbiturates), middle (bilirubin) and high (heme proteins) molecular weight substances.

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REFERENCES [1] [2]

Sharles S. O., Norman S., // J. Immunol. 73 (1984) 41. Safarik I., Safarikova M., in: Hafeli U. (Editor), Scientific and Clinical Applications of Magnetic Carriers, Plenum Press, New York, 1997, p. 24. [3] Stockmann H. B., Hiemstra C. A., Marquet R. I., Ijzermans J. N. // Ann. Surg. 231 (2000) 460. [4] Weber C., Falkenhagen D., in: Hafeli U. (Editor), Scientific and Clinical Applications of Magnetic Carriers, Plenum Press, New York, 1997, p. 371. [5] Komissarova L. Kh., Filippov V. I., Kutushov M. A., in: Hafeli U. (Editor), Scientific and Clinical Applications of Magnetic Carriers, Plenum Press, New York, 1997, p. 380. [6] Gorchakov V. D., Vladimirov V. G. Selective Hemosorbents, Moscow, Medicine, 1989. [7] Fishers R. C., Microsphere Selection Guide, 9025 Technology, March, 2000. [8] Komissorova L. Kh., Gluchoedov N. P., Kutushov M. V., Russian patent No. 2109522, 1998. [9] Widder K., Fluoret G., Senyei A. // J. Pharm Sci. 68 (1979) 79. [10] Komissarova L. Kh., Filippov V. I. // Izv. AN USSR, Ser. Biol. 6 (1988) 78.

In: Chemical and Biochemical Physics: New Frontiers ISBN 1-60021-165-8 Editor: G. E. Zaikov, pp. 47-52 © 2006 Nova Science Publishers, Inc.

Chapter 6

INFLUENCE HEXSAAZOCYCLANES ON A MICROSTRUCTURE OF POLYETHYLENE TEREPHTHALATE O. V. Burykina and F. F. Nijazi Kursk state technical university, Kursk, Russia

ABSTSRACT Research of influence of introduction of hexsaazocyclanes on a microstructure of polyethylene terephthalate is carried out. The increase in ability modified PETP to crystallization, in comparison with not modified PETP, as hexsaazocyclanes play a role of the original centers of crystallization is revealed. Research plasticization effect of hexsaazocyclanes on polyethylene terephthalate is carried out. It is revealed, hexsaazocyclanes introduction influences a maximum of a tangent of dielectric losses polyethylene terephthalate, displacing it aside smaller temperatures.

INTRODUCTION One of the most effective ways of new polymeric materials, obtaining with the properties, given before is modification of known polymers by target additives. Changing chemical structure and quantities of the additive – the modifier, it is possible to improve in a proper way, those operational properties which are required for the given consumer.

EXPERIMENTAL PART Hexsaazocyclanes (HZ), were taken as additives, which have the advanced circuit of interface, high photo stability and thermo stability.

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Figure 1. Structural formulas used hexsaazocyclanes

Availability chromatic groups, allows to use them in addition as dyes of polymers [1]. Proceeding from this, it was represented to us expedient, to compare thermal characteristics of additives and initial polymer, and also to define compatibility of these connections with fusion PETP. Characteristics of the used additives of modifiers are submitted in table 1. Table 1. Characteristics hexsaazocyclanes

ГЦ-1

600

λ макс., nanometer (solvent acetone) 360

ГЦ-2 ГЦ-4

580 454

380 400

Designation

Average molecular weight

Painting of dye

Т fusion, 0С

Т the beginnings of destruction 0С

yellow

305

330

citric beige

327 345

345 330

Temperatures of fusion and the beginning of decomposition hexsaazocyclanes are in limits Тfusion. = 305-3450С and Т destruction. = 330-3450С, that speaks about a potential opportunity of introduction of the given connections in fusion PETP as their thermo stability surpasses temperature of reception and formation PETP. Polyethylene terephthalate modification hexsaazocyclanes by additives was carried out and fibers were formed. Additives introduction did not influence on the process of formation, and, consequently on the polymer fiber properties.

DISCUSSION OF RESULTS For studying structure of polymer and influence of introduction of additives HZ-1; HZ-2; HZ-4 the method of micro photographing has been applied. Cuts of polymeric fibers photographed at 40 multiple increase, on a microscope "Polar" which had a special nozzle for photographing. It follows from the analysis of micro photos (Figure 2-3), that hexsaazocyclanes introduction does not break uniformity of the polymeric structure that speaks about good solubility of hexsaazocyclanes in fusion PETP.

Influence Hexsaazocyclanes on a Microstructure of Polyethylene Terephthalate

49

In a photo of cross-section cut initial PETP fibres (Figure 2) are observed two areas: amorphous and crystal.

Figure 2. Micro photo of a cross-section cut initial PETP: 1) an amorphous part; 2) a crystal part

In crystal area lamellar and fibrillation formations are visible, but they are not advanced enough. The amorphous part occupies great volume from the general space of polymer. On Figure 3 micro photos PETP – the fibers modified HZ-1 (а) are represented; HZ-2 (б); HZ-4 (в), and their cross-section cuts. From comparison of a micro photo initial and modified PETP, it is necessary to note, that modified PETP shows the big tendency to crystallization. In pictures of the fibers painted HZ-1, HZ-2, HZ-4, are visible lamellar and fibrillation formations and are also observed spherallites.

Figure 3. Micro photo of the PETP modified HZ-1 (а); HZ-2 (b) and HZ-3 (с)

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It is well visible in micro photos, that the quantity of an amorphous part of the modified fibers decreases. It raises durability of a fibre and improves his mechanical characteristics as the amorphous area is the most vulnerable for action loadings and pressure as it contains areas of the least order in the macromolecules packing, and the places focusing defects. In micro photos of the modified fibers is the fibrillation structure of a fiber, and visible introduction hexsaazocyclanes in PETP promotes to increase order and density of the structure of the polymer. It was revealed earlier [2], that hexsaazocyclanes additives cause temperature reduction of polyethylene terephthalate fusion, i.e. they have a plasticization effect on polymer. Plasticization proves to be true by measurements of electro physical characteristics at modified polyethylene terephthalate (figure 4).

Figure 4. Dependence of a tangent of a corner of dielectric losses on temperature initial and modified samples PETP: 1-initial PETP;2-PETP+0,1% HZ-2;3-PETP+0,5% HZ-2,4-PETP+3,0% HZ-2

For initial polyethylene terephthalate the maximum of a tangent of dielectric losses (tg δ), corresponding depolsegmentation mobility, is observed at 1150 C. At concentration of the modifier of 1-3 % sharp increase of value tg δ and displacement of a maximum accordingly on 100С and 250С in area of lower temperatures that confirms plasticization action of the modifier is observed. In some works [3, 4] it is supposed, that PETP can have two morphological forms of crystals which define double endothermic effect in the field of fusion. Form I, to which more high-temperature corresponds originally endothermic peak of fusion, has been attributed folded structure, and for the form II responsible for more low-temperature peak of fusion, the crystal structure from more extended circuits has been offered. Thus the length fold forms I causes a degree of perfection of the crystal form II created by partial expansion fold of form I though the nature remains obscure.

Influence Hexsaazocyclanes on a Microstructure of Polyethylene Terephthalate

51

The analysis of micro photos of received samples PETP– fibers has shown, that in the received polymer there are both morphological forms of crystals. Prevalence of one of morphological forms will define, apparently, size of temperature of fusion. On curves DTA initial PETP - fibres and modified hexsaazocyclanes (Figure 5), the peak of fusion represents the area having one maximum that confirms the assumption made earlier of dependence of temperature of fusion from a morphological structure of poly mer.

Figure 5. Curves DТА for unmodified (1) and modified HZ-1 (2), HZ-2 (3) and HZ-4 (4) PETP - fibres

Displacement of peak of fusion on curves DТА in area of smaller temperatures specifies that in the modified fibres crystals have mainly morphological form II (the extended circuits of polymers incorporated into crystallites) while in initial PETP crystals mainly have morphological form I (folded structure). Therefore for initial PETP it is observed endothermic effect at temperature 2690С – speaking by fusion flat folded crystallites (morphological form I). At modified PETP – fibers this effect is observed at temperature 245 – 2630С, it speaks fusion of spherallite (the morphological form II).

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At heating samples PETP on thermogramms the thermal effects, connected with the fusion crystallites, were fixed. On curves DТА modified PETP – fibers it is visible, that at them the breadth of peak of fusion is more, than at initial PETP. Proceeding from the aforesaid, it is possible to admit, that modified hexsaazocyclanes PETP - fibres possess the greater degree crystalline state. It once again confirms the conclusion made earlier, that entered molecules hexsaazocyclanes become the additional centers of crystallization, thus, increasing a degree crystallization modified PETP - fibers.

REFERENCES [1] [2] [3] [4]

Savenkova I.V., Nijazi F.F., Siling S.A., Burykina O.V., Russian polymer news, 2001, vol.6, No.4, s. 61-62. Burykina O.V., Nijazi F.F., Siling S.A., News high schools Chemistry and chemical technology, 2002, vol. 45, No. 5, s. 73-74. Bell P.J., Dumbleton S.H., Polymer Sci., 1969, pt. A-2,V.7,№2, p.1033. Neaiy D.L., Davis T.G., Kibier C.J., J. Polymer Sci., 1970, pt. A-2, V.8, №2, p. 2141.

In: Chemical and Biochemical Physics: New Frontiers ISBN 1-60021-165-8 Editor: G. E. Zaikov, pp. 53-66 © 2006 Nova Science Publishers, Inc.

Chapter 7

FUNCTIONALISING OF LOW-MOLECULAR, OLIGOMER DIENES AND OLEFINS WITH S, O-CONTAINING COMPOUNDS R. Z. Biglova 1, A. U. Galimzjanova 1, V. A. Dokichev 2, G. V. Konesev 3, G. E. Zaikov 4, R. F. Talipov 1 1

Bashkir State University, Ufa, Russia Institute of Organic Chemistry, Ufa Centre of Science, Russian Academy of Sciences, Ufa, Russia 3 Ufa State Petroleum Technical University, Ufa, Russia 4 N.M.Emanuel Institute of Biochemical Physics, Russian Academy of Sciences, Moscow, Russia 2

Functionalization of piperylene fractions, oligodienes and oligoolefins by element sulfur, phenols has been carried out. Functionalized compounds have been shown to be multipurpose additives exhibiting highly antiwear, antiscuff and simultaneously antioxidant and viscous properties. Multipurpose additives to polymers, as well as batch additives to various oils with a complex of necessary properties find increasingly wider application [1, 2]. This fact has resulted in the investigation of element sulfur reactions with dienes, oligodienes and oligoolefins. Cheap and available piperylene fraction (multi-tonnage waste in obtaining isoprene in rubber manufacture), its oligomerization products, as well as oligomerization products of used up buten-isobutane fractions of various molecular weights have been used as initial hydrocarbons. As antiscuff, anti-wear properties of additives depend on the covalent-bonded sulfur contents, the selection of optimum conditions to effect sulfuring processes has been set with introducing the greatest amount possible of covalent sulfur. For this purpose functionalizing of diene and olefin hydrocarbons was conducted on a wide time-temperature mode. Considering that the temperature of boiling piperylene fraction low (42-44ºС), sulfuring was carried out in a constantly temperature-controlled autoclave in the presence of the catalyst cobalt phthalocyanine [3], in the medium of non-polar solvents (for example, heptane). Under

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conditions of synthesis: 130ºС, 3 hrs, >C=С<: S, mole = 1:4 - the product is obtained, with the sulfur amounting to 54.95 mass %, and yield – 10 mass %. The low yield of the target product is due to the experiment going on under static conditions, therefore the next series of experiments was carried out in dynamic conditions. In conducting sulfuring in a constantly rotating autoclave at the same parameters of synthesis, but in the environment of aromatic hydrocarbons (toluene), the yield was 49.5 mass % and the sulfur content went up to 70.35 mass %. Table 1. Sulfuring piperylene fraction with element sulfur in constantly rotating autoclave (V=17 ml), t=130ºC, τ= 3 h Reaction conditions > C=С <: S, mole Solvent Yield of a product, mass. % Sulfur content in a product, mass. %

1 1: 2 toluene

2 1: 1 toluene

3 1: 2 kerosene

4 1: 1 kerosene

5 1: 2 p-xelene

6 1: 1 p-xelene

48.0

24.9

43.0

19.5

100.0

78.6

69.86

48.23

66.11

47.01

68.24

50.71

Piperylene fraction interactions with element sulfur in the absence of the catalyst have improved results (Table.1). At mole ratio > C=С <: S, mole = 1: 2 in p-xelene medium sulfur has reacted quantitatively. The structure of the synthesized compounds is established by a set of methods: NMR-Н1, NMR-С13-spectroscopy and the element analysis. When analyzing the spectra NMR-Н1 signals in the range of 5.50-6.50 мD were detected, that being characteristic of olefin protons. The correlation between the areas of integral curves of olefin and methyl protons enables us to assume the presence of double bonds in the product molecule. This is confirmed by characteristic bands in the IR-spectra, with absorption occurring at 1600 – 1660 cm-1. A signal at 1.10 мD belongs to methyl group protons, and an intense multiplet in the region of 2.10 – 2.50 mD - to methine and methylene protons. In NMR-С13 spectrum at 52.13 mD singlet due to C – S group is found, with the absorption in the area of 600 – 450 cm-1 (- S – S -) within the IR-spectrum. According to the results of analyses, the reaction of piperylene with element sulfur proceeds under the following scheme yielding piperylene bis- tetrasulfide:

CH2-CH=CH-CH-CH3 2 CH2=CH-CH=CH-CH3

+

S8

S4

S4

CH2-CH=CH-CH-CH3 The given scheme is in agreement with the data obtained by authors [3,4] when sulfuring low-molecular dienes, in particular, divinyl. Oligopiperylene (ОPP) with the molecular weight М п=910 was used to study the interaction of oligomerization product of the piperylene fraction with element sulfur. NMRН1, NMR-С13- spectra of a test sample were compared to those given in [5]. The analysis of

Functionalising of Low-Molecular, Oligomer Dienes…

55

chemical shifts and multiplicity signals testifies to the fact that the sample of SROP oligomer (oligopiperylene synthetic rubber) is mainly 1,4-trans-oligomer. Total nonsaturation of the sample makes up 30 %, that corresponding to the presence of four active double bonds in a molecule. The results of determining the number of >C=С< bonds (by bromine number) correlate with the spectral data. The data on interaction of oligopiperylene (ОPP) and oligoisobutylenes (ОIB, М п= 390; 880) with element sulfur are given in Tables 2, 3. According to the results of the element analysis, the contents of sulfur in the obtained products grows both with the rise in the synthesis temperature and with the increase in process length. When the ratio of the initial substances exceeds equivalent mole ratio of oligomers and sulfur, no appreciable change of values of a mass content of sulfur in a product is detected. Modification of oligopiperylene at the temperature over 140ºС results in cross-linking of macromolecules. The reaction with element sulfur in the nonpolar solvent (octane, kerosene) medium does not affect the percentage of sulfur in the product and reduces an opportunity of resinification, and leads to lower sulfur contents in aromatic hydrocarbons. Depending on the product molecular weights and the sulfur content in them, mono- and disulfide bridges can be found in macromolecules. The latter corresponds to the data [4] studying sulfur interaction with isobutylene within the interval between100º to 140ºС. On the example of isobutylene oligomers and a link of oligopiperylene, containing double > C=С < bond the scheme of the processes can be given as: Table 2. Functionalization of oligopiperylene with element sulfur at а) * t = 120ºC; b) * t = 130ºС; c) t =130ºС, τ=8 h. A parameter - the sulfur contents of in a product, mass %

a

b

Conditions of functionalization > C=С <: S, mole 1.00: 0.50 1.00 : 1.00 1.00 : 2.00 1.00 : 3.00 1.00: 0.40 1.00 : 0.50 1.00 : 0.75 1.00 : 1.00 1.00 : 2.00

τ, h 4 0.67 1.15 0.95 0.92 2.23 3.57 3.67 4.19 3.46

c 1.00: 0.05 1.00 : 0.75 1.00 : 1.00 *

Without solvent

octane 1.93 2.21 3.59

6 1.11 2.99 2.87 2.11 2.68 4.02 4.24 5.97 5.67 Solvent pxelene 1.17 1.58 2.21

8 1.69 3.40 3.29 3.16 3.39 4.48 4.77 6.57 6.55 keros ene 2.57 2.76 6.10

56

R. Z. Biglova, A. U. Galimzjanova, V. A. Dokichev et al. Table 3. Functionalization of oligoisobutylene with element sulfur. A parameter - the sulfur contents in a product, mass.%

Conditions of functionalization

> C=С <: S, mole 1.0: 0.8 1.0 : 1.0

1-5 -

М

п

1 2 Solvent (t, ºC) octane1 decane 20ºС 160ºС τ, ч

3

6

6

8

3

1.00 2.61

2.77 3.38

2.81 3.42

2.45 3.06

= 880; 6-8 -

М

п

4

5

6

7

8

- 140ºС

- 160ºС

- 180ºС

6

6

6

6

2.51 3.12

4.14 6.16

4.98 7.00

6.77 7.35

p-xelene 140ºС

= 390.

CH 3 ~CH-CH=CH-CH~

CH 3 2 ~CH 2-CH=CH-CH~

+

S8

Sx ~CH 2

+

S 8-x , x = 1 - 2

CH-CH 2-CH~ CH 3

CH3 CH3 CH3 2 H CH2 C CH2 C CH2 + S8 CH3 n-1

H CH2 C CH2 CH3

CH3 C CH3 n-1 Sx

CH3

+ S8-x,

CH2 C CH C CH2 H CH3 CH3 n-1

n = 7; 16. x = 1-2. Sulfur-containing compounds can acquire antioxidant and anticorrosive properties by introducing the appropriate functional groupings (a fragment of the shielded phenol) into their molecules. Therefore, the following stage of work was modifying oligomers with oxygencontaining compounds (phenol, 2,6-di-tret-butylphenol). The sequence of modification should be as follows: 1) alkylation; 2) sulfuring. The change of the sequence is undesirable, as sulfide bridges have no sufficient durability and can be broken at the subsequent alkylation. Since there are only terminal double bonds in oligoolefin macromolecules, the compositions of sulfur- and alkyl-oligomers as multipurpose additives have been investigated. Alkylation was carried out in nonpolar solvents (octane) in the presence of catalytic systems with reduced relative acidity Na[AlCl4] within 8 hours at the temperature of 100-120ºС at mole ratio >C=С<: phenol: the catalyst, mole= 1:1 : 0.2 according to the forthcoming scheme on the example of isobutylene oligomers and a link of oligopiperylene, containing >C=C<

Functionalising of Low-Molecular, Oligomer Dienes…

57

[6]. The sulfur contents in modified oligopiperylene amounts to 4.92 mass. %, oxygen - 1.58 mass. %. CH3 OH R ~CH2 CH CH CH~ + R

CH3 ~CH2 CH CH2 CH~

Na[AlCl4]

R

CH3 CH3 OH R H CH2 C CH2 C CH2 + R CH3

Na[AlCl4]

OH

R

CH3

CH3

H CH2 C CH3

n-1

CH3

CH2 C n-1 R

OH

R

R= -H; -But. n = 7; 16.

Table 4. Interaction of sulfur with 4-oligoisobutenylphenols in the polar solvent medium t = 145-150ºC, τ =6 h Conditions of interaction Phenol: S8, mole Solvent

1

2

3

4

5

6

1.0: 1.5

1.0: 1.0 DMF+ pxelene

1.0: 0.5 DMF + pxelene

1.0: 0.5 DMF+ ТHF

1.0: 0.5 DMSO+ p-xelene

1.0: 0.3 DMSO+ p-xelene

Initial oligoisobutylene ( М п = 390) Yield of a product, 21.0 18.0 mass % Sulfur content in a 8.39 6.09 product, mass%

42.0

34.0

28.0

46.0

6.46

6.15

3.92

3.50

Initial oligoisobutylene ( М п = 880) Yield of a product, 29.0 30.7 mass % Sulfur content in a 1.24 1.86 product, mass %

96.0

41.0

65.0

72.6

3.76

0.63

1.40

0.73

DMF

Functionalization of oligoisobutylenes with phenols was also performed by an alternative technique in the polar solvents medium (DMF, DMSO) in which the reaction of sulfur with low-molecular phenols was conducted [5]. Pre-alkylated phenols (4-oligoisobutenylphenols) and element sulfur acted as the initial substances The interaction was carried on in the inert nitrogen flow (with releasing hydrogen sulfide removed from the reaction zone) at 140150ºС. The experiment results are given in Table 4. p-xelene, THF, was added in the reactant

58

R. Z. Biglova, A. U. Galimzjanova, V. A. Dokichev et al.

mixture for better solubility. The ratio of solvents in the relation to the initial phenol weight is phenol: DMF (DMSO): p-xelene (THF),mass. = 1:4:1. It is experimentally found, that in the DMF environment the reaction proceeds with greater yield than in that of DMSO. With the ratio of initial substances lowered the yield of the product grows, however at ratios smaller than 1.0:0.5, the sulfur contents in the end compound turns out to go down. Relative viscosities of modified oligomers, determined by viscosimetry technique, are somewhat higher than the values of the respective initial oligomers (Table 5). The observed phenomenon allows to believe, that in the interaction of oligomers with phenols and element sulfur there occurs an increase in molecular weight due to the functionalised product generated. Table 5. Viscosity characteristics of initial and оf functionalized oligomers Oligomer

ηrel

c, g/dl 4.2 1.0 4.2 1.0 4.2 1.0 4.2 1.0 4.2 1.0 4.2 1.0

Oligoisobutylene ( М п = 390) Sulfured 4-oligoisobutenylphenol Oligoisobutylene ( М п = 880) Sulfured 4-oligoisobutenylphenol Oligopiperylene ( М п = 910) Sulfured oligopiperylene

1.14 1.03 1.41 1.32 1.33 1.19 1.92 1.48 1.42 1.26 2.29 1.67

According to the element analysis results, the determination of modified oligomer relative viscosities, to the spectra data and references [7], the scheme of interaction of oligoisobutylene-alkylated phenols with element sulfur in our case can be written in the following way: CH3 H CH2 C CH3

CH3 CH2 C CH3 + S8 n-1

CH3 CH3 H CH2 C CH2 C CH3 CH3 n-1

OH

OH + H2S + S7-x,

Sx CH3 H CH2 C CH3 n = 7; 16. x = 1-2.

CH3 CH2 C n-1

CH3

OH

Functionalising of Low-Molecular, Oligomer Dienes…

59

The demand for multi-purpose additives in the petrochemical industry is a common knowledge. Functionalized S-,O-containing oligomers were investigated as additives. Motor oils contain up to 10 % of additives differing in their functional effects to ensure long-term efficiency. These additives should protect oil-lubricated surfaces, improve oil properties and preserve the oil composition. According to the listed parameters certain classes of chemical compounds providing necessary properties are applied. Antiwear, antiscuff properties of S-containing compounds on the basis of piperylene fractions have been investigated. To characterize the designated properties of additives the following important parameters have been employed: rate of wearing (аm) and factor of friction (kfr). Testing sulfur-containing substances to withstand washing liquors (clay solution) and lubricants have been performed on МТ3 experimental installation according to the technique described in [8]. Depending on the applied loading the rates of wearing the cores from chisel steel in compositions on the basis of mark 52 cylinder oil in the presence of the synthesized substances have been determined. In comparison with VNIINP-354 additive traditionally employed in the industry (zinc o-,o- di(octylphenyl)-dithiophospate), produced piperylene bis-tetrasulfide and sulfur-modified oligopiperylene have displayed high results (Figure 1).

Figure 1. Dependence of wearing rate on applied loading; 1. industrial oil of mark 52 – VNIINP-354; 2. industrial oil of mark 52 - piperylene bis- tetrasulfide; 3. industrial oil of mark 52 - sulfured oligopiperylene;

Studying the antiwear properties of clay solutions in the presence of an insignificant amount (up to 1 mass.%) of sulfur-containing product and up to 3 mass.% of SAS (SDBUR) has shown that the increase in the contacted pressure results in the values of the factor of friction and wearing rate of the cores from chisel steel going down by 30-35 % as compared with the respective parameters for the clay solution without additives (Figures 2,3). As the

60

R. Z. Biglova, A. U. Galimzjanova, V. A. Dokichev et al.

values of axial loading increase, films are formed on the surface under friction that leading to greater efficiency of drilling fluids at higher loadings. The operational parameters have been found to be affected by the order the components are mixed. The compositions of a clay solution with xylene solution of sulfured piperylene fraction to some extent increase the values of wearing rate and friction factor in contrast to a product in the absence of the solvent. Tests of an oil composition in the presence of synthesized piperylene bis- tetrasulfide were performed on twenty chisels of drills under the conditions of the Far North. Antioxidant properties of oil with additives on the basis of oligopiperylene have been determined by stability measurement method on the induction period of deposition (IPD). Thermal stabilizing ability of sulfured oligopiperylenylphenol on adding it into industrial oil of I-20 mark is within the limits satisfying All-Union Standard (the contents of Х0 precipitation is under 0.5 mass %). The given compositions were also tested for viscosity properties. The index of viscosity should be no less than 90 to produce thickening action, that being confirmed by the data given in Table 6.

Figure 2. Dependence of wearing rate on applied loading; 1. a clay solution; 2. a clay solution – SDBUR (1.0 mass.%); 3. a clay solution – SDBUR (1.0 mass.%) - piperylene bis- tetrasulfide (0.1 mass.%); 4. a clay solution – SDBUR (1.0 mass.%) - piperylene bis- tetrasulfide in solvent (0.1 mass.%).

Table 6. Characteristics of oil I- 20 in the presence of additives

Additive Oligopiperylene ( М п=910) Sulfuring 2,6-di-But-4oligopiperylenyl phenol Oil I-20

Additives concentration in oil, mass. %

Viscosity (cc) at 40ºС

100ºС

2 5

74.2 84.7

2 5 -

81.0 103.3 66.7

IV

Deposit, mass. % (IPD)

9.1 10.3

95 98

-

10.1 11.4 8.3

96 100 91

0.22 0.85

Functionalising of Low-Molecular, Oligomer Dienes…

61

Figure 3. Dependence of friction factor on applied loading; 1. a clay solution; 2. a clay solution – SDBUR (1.0 mass.%); 3. a clay solution – SDBUR (1.0 mass.%) - piperylene bis- tetrasulfide (0.1 mass.%); 4. a clay solution – SDBUR (1.0 mass.%) - piperylene bis- tetrasulfide in solvent (0.1 mass.%).

Detergent-dispersive additives are indispensable components of batch additives. Imides of amber acid, whose washing action is considered in the aspect of their solubilizing capacity, i.e. transferring with micelles into a solution of SAS products, insoluble in the given medium are most common in this quality. The influence of oxidation inhibitors (oligoolefynylphenol, oligodienylphenol), antiwear additives (sulfuring oligomers of isobutylene and piperylene), chemicals-additives of multifunctional action (oilgoolefin- and oligodiene- alkylated phenol products and products of subsequent sulfuring of the obtained compounds both in non polar, and in polar solvents) on detergent-dispersive efficiency of cuccinimide has been investigated in order to find the optimum concentration of the compounds within a batch. According to [9], the concentration dependences of antiwear efficiency of sulfur-containing compounds are of a complex extreme character accounted for by micelle formation in the additive oil solution. From this point of view it is interesting to investigate the concentration dependences of the antiwear and detergent-dispersive additive compositions. Cuccinimide necessary for studying solubilization is synthesized on the basis of oligoisobutylene ( М п = 880) by known technique [10] and the contents of nitrogen in it is about 3.98 mass.% (according to TU- 38101146-77 the contents should be no less than 1.4 mass.%). The research into solubilization abilities of additives was carried out by the technique described in [11]. In relation to the dye the solubilizing action was to a greater or lesser extent displayed by all types of the investigated compounds. The curves of the composition solubilization effect (SE) dependence on additive concentrations are of a complex extreme character; also do they differ in their location in relation to the axes of coordinates. For the majority of substances dependence curves have three strongly

62

R. Z. Biglova, A. U. Galimzjanova, V. A. Dokichev et al.

pronounced areas. The first covers an interval of concentrations with no solubilization effect, the second - promotes the growth of solubilization ability due to the change of the additive content, and the third is the area of higher concentration with the maximum values of the effect. It is because of the fact that in each specified areas additive solutions exhibit various colloid properties. In experiments with rhodamine C mainly two types of curves (Figures 4 a, b, c, d) were constructed: the first is characterized by fast colloid dissolution of dye and the solution stability (e.g., curves 2b, 3b); the other – by a longer stabilization period of solutions (curves 2а, 3а), but with a sharp growth of solubilization effect for compositions in the area of the higher concentration (curve 9 а). For the compositions of the specified additives with cuccinimide the solubilization effect was more evident and the values of critical micelle concentration (CMC) were lower as compared with the features of individual substances in isooctane (Table 7). If sulfured piperylene fractions are characterized by the CMC interval of 0.05-0.45 mass.%, in the presence of 0.5 and 1.0 mass.% of cuccinimide the CMC areas correspond to the following values: 0.02-0.50 and 0.01-0.50 mass.%.

Figure 4а) Modified oligoisobutylene ( М п= 880); 1. cuccinimide; 2. sulfured oligoisobutylene; 3. sulfured oligoisobutylene - cuccinimide (0.3 mass.%); 4. 2,6-d i-But-4-oligoisobutenylphenol; 5. 2,6-d i-But-4oligoisobutenylphenol - cuccinimide (0.3 mass.%); 6. 2,6-di-But-4-oligoisobutenylphenol: sulfured oligoisobutylene, mass. = 1 : 1; 7. 2,6-d i-But-4-oligoisobutenylphenol: sulfured oligoisobutylene, mass. = 1 : 1 - cuccinimide (0.3 mass.%); 8. Sulfur-containing bis- 4,4 `-oligoisobutenylphenol; 9. Sulfur-containing bis4,4 `-oligoisobutenylphenol - cuccinimide (0.3 mass.%);

Functionalising of Low-Molecular, Oligomer Dienes…

63

figure 4b) Modified oligoisobutylene ( М п= 390) 1. cuccinimide; 2. sulfured oligoisobutylene; 3. sulfured oligoisobutylene - cuccinimide (0.3 mass.%); 4. 2,6d i-But-4-oligoisobutenylphenol; 5. 2,6-d i-But-4-oligoisobutenylphenol - cuccinimide (0.3 mass.%); 6. 2,6di-But-4-oligoisobutenylphenol: sulfured oligoisobutylene, mass. = 1 : 1; 7. 2,6-d i-But-4oligoisobutenylphenol: sulfured oligoisobutylene, mass. = 1 : 1 - cuccinimide (0.3 mass.%); 8. Sulfurcontaining bis- 4,4 `-oligoisobutenylphenol; 9. Sulfur-containing bis- 4,4 `-oligoisobutenylphenol cuccinimide (0.3 mass.%);

Figure 4c) Modified oligopiperylene 1. cuccinimide; 2. sulfured oligopiperylene; 3. sulfured oligopiperylene - cuccinimide (0.3mass.%); 4. 2,6-di But-4-oligopiperylenylphenol; 5. 2,6-di -But-4-oligopiperylenylphenol - cuccinimide (0.3mass.%); 6. sulfured 2,6-di -But-4-oligopiperylenylphenol; 7. sulfured 2,6-di -But-4-oligopiperylenylphenol - cuccinimide (0.3mass.%);

64

R. Z. Biglova, A. U. Galimzjanova, V. A. Dokichev et al.

Figure 4d) sulfured piperylene fraction 1. cuccinimide; 2. piperylene bis-tetrasulfide; 3. piperylene bis-tetrasulfide - cuccinimide (0.5 mass.%); 4. piperylene bis-tetrasulfide - cuccinimide (1.0 mass.%); Figure 4. Dependence of solubilizing power on additive concentration in a solution.

Table 7. Critical micelle concentration of functionalized products, mass. % Additive Cuccinimide Sulfured oligomer Sulfured oligomer - cuccinimide (0.3 mass. %) Alkylated 2,6-di -But-phenol Alkylated 2,6-di -But-phenol cuccinimide (0.3 mass. %) Product of successive alkylation and sulfuring in nonpolar solvents Product of successive alkylation and sulfuring in nonpolar solvents cuccinimide (0.3 mass. %) Product of successive alkylation and sulfuring in polar solvents Product of successive alkylation and sulfuring in polar solvents - cuccinimide (0.3 mass. %)

ОPP ( М п=910) 0.08 - 0.42 0.09 - 1.30

ОIB ( М п=880) 0.08 - 0.42 0.10 - 1.90

ОIB ( М п=390) 0.08 - 0.42 0.09 - 0.30

0.08 - 0.70

0.08 - 1.70

0.08 - 0.20

0.20 - 1.80

0.30 - 3.00

0.20 - 2.20

0.08 - 1.60

0.10 - 2.40

0.10 - 1.40

0.09 - 0.56

0.10 - 2.40

0.16 - 2.20

0.09 - 0.30

0.10 - 2.20

0.08 - 2.10

-

0.15 - 0.95

0.07 - 1.00

-

0.03 - 0.09

0.04 - 0.09

Influence of size and structure of a hydrocarbon radical of antioxidant and antiwear additives introduced in the oil composition on cuccinimide detergent-dispersion action is observed. The maximum solubilization effect takes place for the ramified and smaller-size radicals. Such an effect is discovered in the substances synthesized on the basis of

Functionalising of Low-Molecular, Oligomer Dienes…

65

oligopiperylene ( М п=910) and oligoisobutylene ( М п=390). Apparently, the phenomenon is accounted for by the fact that in the inverse emulsions such as «water in tar» the increase in length of the hydrocarbone substitute by one -СН2-group in the given homologous row leads to the critical micelle concentration shift into the area of larger values. The sulfur contents increase in functionalized samples contributes to narrower CMC interval and its shift into the area of smaller values (Figure 4 d: sulfured piperylene fraction containing 47.01 mass % of sulfur). The experimental data (Table 7) testify that the introduction of the synthesized substances in an oil composition with cuccinimide allows to considerably cut a dosage of the latter to maintain operational characteristics on a sufficiently high level.

CONCLUSIONS Functionalization of piperylene fractions, oligodienes and oligoolefins by element sulfur has been carried out, optimum conditions to effect their interaction introducing the greatest possible quantity of sulfur have been selected. Functionalized compounds have been shown to be multipurpose additives exhibiting highly antiwear, antiscuff and simultaneously antioxidant and viscous properties. Influence of the obtained sulfur-containing substances and the shielded phenols on detergent-dispersive action of cuccinimide has been investigated. It has been established, that combination of antiwear and antioxidant additives in an oil composition with cuccinimide allows to appreciably reduce the contents of the latter to maintain sufficiently high operational characteristics of lubricants.

REFERENCES [1] [2] [3] [4] [5]

[6]

[7]

B.A.Sobolev. Manufacture and consumption of additives in Russia.// Mir nefteproductov. – 2000. - №2. – p.1-2. I.E.Selezneva, A.J.Levin, S.V.Monin. Detergent-dispersion additives to motor oils. // Khim. i tekhnol. topl. i mas. - 1999. - № 6. - p.39-43. M.G.Voronkov, N.A.Vjazankin, E.N.Derjagina etc. Reactions of sulfur with organic compounds./pod red. M.G.Voronkova. - Novosibirsk: Nauka. - 1979. - p. 368 S.Oae. Chemistry of organic compounds of sulfur: transl. Japan./pod red. E.N.Prilezhaevoj.- M.: Khimiya. - 1975. S.A.Egoricheva, V.A.Rozentsvet, B.I.Pantuh, M.V.Eskina, A.S.Hachaturov, R.M.Livshits. Molecular characteristics of oligopiperylene, obtained by cationic polymerization. // Neftekhim.prom. - 1982. - №8. - p.12-13. R.Z.Biglova, V.P.Malinskaja, K.S.Minsker. Polymer-analogous reactions of polyolefins with phenols and aminophenols. // Vysokomol. Soedin.-1994. - vol.36А.- № 8. - p.12761280. S.V.Buharov, L.V.Konoshenko, S.E.Solov'eva et al. Interaction of sulfur with 2,6-di tret-butylphenol in dipolar aprotic solvents. // Zh. Obshch. Khim.- 1999. - vol.69. – iss.1. - p.130-133.

66 [8]

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G.V.Konesev, M.R.Mavljutov, A.I.Spivak, R.A.Ismagilov. Lubricant action of medium in chisel technology. - M.: Nedra. - 1993. – p.46-50. [9] N.N.Loznetsova, K.A.Pavlov, J.P.Toporov, G.G.Shchegolev. A role of micelle formation in displaying antiwear properties in lubricant oils. // Tezisy dokl. II Mezhd.Confer. «Colloid-2003» - 2003. – p.184. [10] O.L.Glavati, T.D.Popovich, V.T.Borislavsky, A.S.Zhurba, A.N.Lukashevich. Improvement of quality of cuccinimide additives. // Khim. i tekhnol. topl. i mas. - 1989. - № 3. - p.22-24. [11] A.B.Vipper, S.E.Krein, V.V.Sher, P.I.Sanin. Solubilizing action of additives of a various structure and its influence on properties of lubricant oils. //Neftekhim. - 1968. vol.5. - № 5. – p.798-806.

In: Chemical and Biochemical Physics: New Frontiers ISBN 1-60021-165-8 Editor: G. E. Zaikov, pp. 67-72 © 2006 Nova Science Publishers, Inc.

Chapter 8

FRACTAL MODEL OF STABILITY TO THE CRACKING OF MODIFIED POLYETHYLENE A. Kh. Malamatov and G. V. Kozlov Kabardino-Balkarian State University, Nal’chik, Russia

ABSTRACT It is shown, that the criterion of polyethylenes samples fracture in tests on cracking under stress in active environments is reaching by polar liquid of sample median plane. Stability to cracking is correctly described within the framework of fractal model of transport processes in polymers. The cause of extreme raising of stability to cracking are structural changes, which are due to introduction of high disperse mixture Fe/FeO and characterizing by the dimension of excess energy localization regions.

Keywords: polyethylene, modification, diffusion, voids, brittle fracture.

INTRODUCTION The term “cracking at simultaneous action of stress and environment” was introduced for the description of polymers (mainly polyethylenes) brittle fracture, which are present in a stressed state in the presence of mobile polar liquids. It was shown [1], that, what all is said and done, for material strength at this fracture mode is responsible the weakest amorphous part of semi-crystalline polymer. This allows to connect occurring at cracking phenomenon with polar liquid diffusion into amorphous regions. The authors [2] found, that in case of high density polyethylene (HDPE), modified by high disperse mixture Fe/FeO (Z), is observed strong extreme rise of stability to cracking expressed by the time up to fracture τ50. So, if for the initial HDPE normative value τ50.is equal to 10 hours, then for composition HDPE+Z with content Z CZ=0.05 mass.% the value τ50 reaches 250 hours. The purpose of the present paper is the explanation of this important

68

A. Kh. Malamatov and G. V. Kozlov

effect both from theoretical and practical points of view within the framework of fractal conception of transport processed.

EXPERIMENTAL The gasphase HDPE of industrial production mark 276 with average weight molecular weight M w ≈ 1,5 × 10 5 and crystallinity degree 0,68, determined by samples density, is used. The method of processing of compositions HDPE+Z samples in paper [3] was expounded. The initial HDPE and its compositions with contents Z within the interval 0,01÷1,0 mass.% were used. The figures in conditional designation of compositions HDPE+Z mean content of Z in mass%. The tension tests were made on film samples with thichness 0,06÷0,08 mm, width 5 mm and base length 40 mm. The samples were made by hot pressing at temperature 463 K and pressure ~5MPa. The testing is made at temperature 323 K and strain rate 2,7×10-3s-1. The test on stability to cracking under stress was made accoring to the standard (GOST 13 518-68) on samples, cutting out from plates, which were made by hot pressing. The sample sizes corresponded to the mentioned above standard. Before testing sample was placed in conductor socket and by handle pressure on it the notch of length 0,1 mm was made. Then each sample was bent in special arranging so that, the notch was placed on the outside and put in the holder. One holder maintains 10 samples [2]. Then holder with samples was placed in the bath with active environment (20%-th aquatic solution of OP-7, GOST 8433-57), which were placed in thermostat with temperature 323÷0,5 K. Samples examining was made visually during first two days every each hour and further two times in one day. As stability of polyetylenes to cracking is adopted the time in hours from testing beginning up to appearance of cracks of 50% samples (τ50) [2].

RESULTS AND DISCUSSION For theoretical prediction of value τ50, characterizing stability to cracking, two main assumptions will be made. Firstly, it is assumed, that the samples fracture occurs, when active environment in diffusion process reaches their median plate. This assumption is based on the analysis of cracking under stress process [1]. Then theoretical value τ50

(τT50 )

is expressed

by the basic equation of stationary diffusion [4]:

l2 , τ = GD T 50

(1)

where l is one half of sample thichness, which is equal in our case to 2 mm, D is diffusivity of active environment in HDPE.

Fractal Model of Stability to the Cracking of Modified Polyethylene

69

The second assumption consists in the fact, that the diffusion of water molecules clusters without consideration of the molecules OP-7 sizes is considered. As a matter of fact, this means, that in cluster of molecules H2O is assumed the replacement of one of these molecules on molecule OP-7. The clusterization of water molecules at interaction with polymer is a well known fact [5, 6]. The estimations show, that in this case the cluster consists of three molecules H2O [6]. The schematic representation of water cluster according to the data of paper [5] is shown in Figure 1. This scheme allows to calculate the largest size of cluster dm≈7,8 Å allowing, that water molecule diameter is equal to 3,08 Å [5].

Figure 1. The model of adsorbed by polymer water molecules cluster [5].

d H 2O

is diameter of water

molecule, dm is calculated diameter of water cluster.

For a calculation of the diffusivity D the fractal model of transport processes [7] will be use, according to which the value D is equal to:

D = D0′ f g (d h d m ) 2 ( Dt −d s ) d s , where

D0′

(2)

is a universal constant, which is equal to 3,7×10-7 cm2/s, fg is relative free volume,

dn is diameter of this volume microvoid, Dt is polymer structure dimension, controlling the transport processes, ds is spectral dimension, adopted for linear HDPE equal to 1,0 [8]. The choice of dimension Dt depends on the value of relation dh/dm [9]. At dm<0,6dh interaction of diffusant molecules with walls of free volume microvoid is small and transport process is controlled by fractal dimension of structure df (structural transport). At dm≤0,6dh on transport processes has strong influence interaction of diffusant molecules with walls of free volume microvoid, which are polymeric macromolecules surface with dimension Df (Df is the dimension of excess energy localization regions) [10]. In this case Dt=Df (molecular transport) [9] is adopted. Let’s consider the methods of parameters estimation which enter the equation (2). The value fg can be determined according to the equation [10]:

70

A. Kh. Malamatov and G. V. Kozlov

 1+ ν , f g = 0,017   1 − 2ν 

(3)

where ν is Poisson’s ratio, defined according to the results of mechanic testing with the aid of the relationship [11]:

σY (1 − 2ν) , = E σ(1 + ν)

(4)

where σY is yielding stress, E is elasticity modulus. The dimension Df is calculated according to the following equation [12]:

Df =

2(1 − ν) . 1 − 2ν

(5)

The volume of free volume microvoid νh within the framework of fractal model [10] can be calculated according to the equation:

νh =

D f (1 − 2ν)kTm

,

(6)

fg E

where k is Boltzmann constant, Tm is polymer’s melting temperature (for HDPE Tm=403 K [13]), and then to estimate the diameter of this microvoid dh from geometric opinions. The values of Df and dh for studied compositions HDPE+Z in table 1 are cited. The value dh can be compared with corresponding experimental data obtained by positrons annihilation method. For HDPE at T=323 K experimental value is dh≈6,8 Å [14]. This value dh corresponds well enough with corresponding calculated values dh cited in table 1. Now we can calculate the value D according to the equation (2) (table 1) and then theoretical value of stability to cracking of experimental values

τl50

and

τT50

τT50

according to the equation (1). The comparison

in table 1 is cited. As can be seen, the good

correspondence of theory and experiment is obtained – the average discrepancy

τl50

and

τT50

is equal to ~9%. Allowing for statistical character of testing on cracking in active environments, it can be said, that this discrepancy is not exceeded the experimental error. It is important to note, that at calculation

τT50

the fitted empirical constants were not used and

extreme change τ50 is fully explained by structural changes, due to introduction Z and characterized by dimension Df. Besides, the correspondence of theory and experiment confirms the correctness of the made above assumptions. Let’s consider structural aspect of τ50 change due to introduction Z. As it is known [3, 15], for compositions HDPE+Z is observed the extreme rise of relative fraction of local order regions (clusters) ϕcl, that results to decrease of fractal dimension of structure df according to the equation [15]:

Fractal Model of Stability to the Cracking of Modified Polyethylene

71

12

 ϕ  d f = 3 − 6 cl  ,  SC∞ 

(7)

were S is cross-sectional area of macromolecule,

C∞

is characteristic ratio, which is an

indicator of polymeric chain statistical flexibility [16]. In its turn, dimensions df and Df are connected by the relationship [12]:

Df = 1+

1 3− df

.

(8)

Hence, the reduction df results to decrease Df that is the main factor defining the diffusivity D reduction (the equations (2) and (6)) and, as consequence, τ50 rise (the equation (1)). It will be noted also, that comparatively small variation Df (about 20%) determines strong (eightfold) change D and, as consequence, τ50 in virtue of power-type dependence of the equation (2) typical for fractal relationships.

CONCLUSIONS Therefore, the results of the present paper have shown, that the criterion of polyethylenes samples fracture in tests on cracking under stress in active environments is reaching by polar liquid of sample median plane. Stability to cracking is correctly described within the framework of fractal model of transport processes in polymers. The cause of extreme raising of stability to cracking are structural changes, which are due to introduction of high disperse mixture Fe/FeO and characterized by the dimension of excess energy localization regions. Table 1. The characteristics of diffusion process of active environment for compositions HDPE+Z The composition

Df

dh, Å

D×108, cm2/s

HDPE

τl50 , hours

τT50 , hours

10 5,17

8,65

38,6

4,76 (normative)

HDPE+0,01Z

5,0

8,56

4,11

36

44,1

HDPE+0,05Z

4,33

6,65

0,69

250

268

HDPE+0,10Z

5,0

8,56

4,11

38

44,1

HDPE+0,15Z

5,17

8,65

4,76

37

38,6

HDPE+1,0Z

5,17

8,65

4,76

39

38,6

72

A. Kh. Malamatov and G. V. Kozlov

REFERENCES [1] [2] [3]

[4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16]

Howard J.B. In book: Engineering Design for Plastics. Ed. Baer E. London, Chapman and Hall, LTD., 1966, p. 331-378. Mashukov N.I., Krupin V.A., Mikitaev A.K., Malamatov A.Kh. Plast. Massy, 1990, №11, p. 31-32. Mashukov N.I., Sedyuk V.D., Kozlov G.V., Ovcharenko E.N., Gladyshev G.P., Vodachov A.B. Stabilization and Modification of Polyethylene by Oxygen Acceptos. (Preprint). Moscow, IchF AN SSSR, 1990, 64 p. Rogers G.E. In book: Engineering Design for Plastics. Ed. Baer E. London, Chapman and Hall, LTD., 1966, p. 193-273. Belford G., Sinai N. In book: Water in Polymers, Ed. Rowland S.P. Washington, D.C., 1980, p. 314-335. Brown G.L. In book: Water in Polymers, Ed. Rowland S.P. Washington, D.C., 1980, p. 419-428. Kozlov G.V., Zaikov G.E. Vysokomolek. Soed. B, 2003, v. 45, №7, p. 1197-1201. Alexander S., Orbach R. J. Phys. Lett. (Paris), 1982, v. 42, №17, p. L625-L631. Kozlov G.V., Afaunov V.V., Mashukov N.I., Lipatov Yu.S. Doklady AN Ukraine, 2000, №10, p. 140-145. Kozlov G.V., Sanditov D.S., Lipatov Yu.S. In book: Uspekhi v Oblasti Fiziko-Khimii Polimerov. Ed. Zaikov G.E. a. a. Moscow, Khimiya, 2004, p. 412-474. Kozlov G.V., Sanditov D.S. Anharmonic Effects and Physical-Mechanical Properties of Polymers (in Russian). Novosibirsk, Nauka, 1994, 261 p. Balankin A.S. Synergetics of Deformable Body (in Russian). Moscow, Publishers of Ministry of Defence SSSR, 1991, 404 p. Kalinchev E.L., Sakovtseva M.B. Properties and Processing of Thermoplasts (in Russian). Leningrad, Khimiya, 1983, 288 p. Lin D., Wang S.J. J. Phys.: Condens. Matter, 1992, v. 4, №12, p. 3331-3336. Kozlov G.V., Zaikov G.E. Structure of the Polymer Amorphous State. Utrecht-Boston, Brill Academic Publishers, 2004, 465 p. Budtov V.P. Physical Chemistry of Polymer Solutions. Sankt-Peterburg, Khimiya, 1992, 384 p.

In: Chemical and Biochemical Physics: New Frontiers ISBN 1-60021-165-8 Editor: G. E. Zaikov, pp. 73-78 © 2006 Nova Science Publishers, Inc.

Chapter 9

THE THEORETICAL DESCRIPTION OF MODIFIED POLYETHYLENE THERMOSTABILITY WITHIN THE FRAMEWORK OF ANOMALOUS DIFFUSION MODELS A. Kh. Malamatov and G. V. Kozlov Kabardino-Balkarian State University, Nal’chik, Russian Federation

ABSTRACT It is shown that the applicability of fractal model of anomalous diffusion for quantitative description of thermogravimetric analysis results in case of high density polyethylene modified by high disperse mixture Fe/FeO (Z). It is shown the influence of diffusion type on the value of sample 5%-th mass loss temperature and was offered structural analysis of this effect. The critical content Z it is determined, at which degradation will be elapse so, as in inert gas atmosphere.

Keywords: polyethylene, modification, thermal properties, diffusion, structure – property relation.

INTRODUCTION It is known [1], that the intensive thermal degradation temperature Td characterizes the polymer’s thermostability. As the characteristic of thermostability according to [2] “limiting temperature is accepted at which chemical change of polymer reflected on its properties” takes place. The thermostability is determined with the aid of thermogravimetric analysis (TGA). Hereafter under Td a sample of 5%-th mass loss temperature obtained in TGA testing will be understand. The importance of the parameter Td defined vast enough literature dedicated to studies of the dependence Td on polymers characteristics. Nevertheless, these studies allow for Td

74

A. Kh. Malamatov and G. V. Kozlov

interrelation only with chemical constitution in that or other variant: the presence of “weak chains” [5], those or other groups in polymeric chain [4], defects of polymeric chain [5] and so on. However, physical structure of polymeric materials in all these cases is not allowed for, though the authors [6] have shown, that for films of polycarbonate based on the bisphenole A (PC) obtained from various solvents (that assumes invariability of polymer chemical constitution) the values Td distinction can reach 120 K. This result assumes strong influence of polymer structure at testing temperature on its thermostability. Earlier it was found [7], that the introduction of high disperse mixture Fe/FeO (Z) in high density polyethylene (HDPE) results to essential (about by 100 K) raising Td in comparison with initial polymer. Therefore, the purpose of the present paper is to study the influence Z on thermostability of composition HDPE+Z. As a theoretical basis of studies anomalous diffusion model [8] was used.

EXPERIMENTAL The gasphase HDPE of industrial production mark 276 with average weight molecular weight

M w ≈ 1,5 × 10 5

and crystallinity degree 0,68, determined by sample density, is

used. The method of processing of compositions HDPE+Z sample was expounded in paper [7]. The initial HDPE and its compositions with contents Z within the interval 0,01-1,0 mass.% were used. The tension tests were made on film samples with thickness 0,06-0,08 mm, width 5 mm and base length 40 mm. The samples were not produced by pressing at temperature 463 K and pressure ~5MPa. The testing is made at temperature 293 K and strain rate 2,7×10-3s-1. The experimental estimation of fractal dimension df of compositions HDPE+Z structure is carried out according to the equation [9]:

d f = (d − 1)(1 + ν) ,

(1)

where d is dimension of Euclidean space, in which fractal is considered (obviously, in our case d=3), ν is Poisson’s ratio, the value of which can be estimated according to the results of mechanical testing with the aid of the relationship [10]:

σY 1 − 2ν , = E σ(1 + ν )

(2)

where σY is yielding stress, E is elasticity modulus. The thermostability of compositions HDPE+Z samples have been researched on derivatograph of model “DuPont-951” (USA) in dynamic regime in air and in inert gas (helium) atmosphere. The heating rate is equal to 5 K/min within temperatures interval 293750 K. The samples weighing are varied in limits 4,295-4,857 mg. The melting temperatures Tm for considered compositions are accepted according to the data of paper [7].

The Theoretical Description of Modified Polyethylene Thermostability…

75

RESULTS AND DISCUSSION As it is known [11], for strange (anomalous) diffusion on fractal objects its two main types can be select: slow and rapid diffusion. At the basis of such division the dependence of mobile reagent displacement s on time t [11] was appointed:

S ~ tβ ,

(3)

where for classical case β=1/2, for slow diffusion β<1/2 and for rapid diffusion - β>1/2. As it was demonstrated in paper [12], most precisely the polymeric melt structure in high temperatures region, corresponding to Td, can be characterized by macromolecular coil dimension ∆f. Further the condition ∆f=df [13] will be accept. Earlier within the framework of fractional derivatives theory the interrelation ∆f and β was shown, which analytically was expressed as following [11]:

β=

∆ f −1 4

(4)

for slow diffusion and

β=

∆ f −1 ∆f

(5)

for rapid diffusion. The structural boundary between mentioned diffusion types follows to consider the value ∆f=2,5 at overall variation 2,0≤ <3: at ∆f<2,5 (less compact macromolecular cols) is realized rapid diffusion of oxidant (oxygen), at ∆f>2,5 – slow diffusion [11]. For theoretical estimation of value T5% the following equation [14] is used:

∆ f = C (T5% − Tm ) β ,

(6)

where c is constant, accepted equal to 0,093 for rapid diffusion and 0,305 – for slow diffusion [14]. The equation (6) defines three factors, affecting on polymeric materials thermostability: polymer chemical constitution, characterized by value Tm; structure of polymeric meet, characterized by dimension ∆f and type (intensity) oxidant diffusion, connected with structure and characterized by exponent β [14]. In a Figure 1 the theoretical dependences T5% on contents Z CZ for cases of slow and rapid diffusion of oxidant and also experimental magnitudes T5%, obtained in air and in helium atmosphere are shown. As follows from the data of this figure, the value T5% for initial HDPE corresponds to slow diffusion case and for compositions HDPE+Z – to rapid diffusion.

76

A. Kh. Malamatov and G. V. Kozlov

Attention it is draw the fact, that the experimental values T5% are above theoretical and this discrepancy increases at contents Z raising. For values T5%, obtained in helium atmosphere, where in virtue of absence of external oxidant diffusion processes do not play any role, the condition T5%=const=708±4 K is carried out, that ought to be expected.

Figure 1. The dependences of 5%-th mass loss temperature T5% in TGA testing on Z contents CZ for compositions HDPE+Z. The calculation according to the equation (6) for slow (1) and rapid (2) diffusion; experimental TGA data in air (3) and in helium atmosphere (4).

Let’s consider the physical basis of the change of diffusion regime from slow (subdiffusive) up to rapid (superdiffusive). Anomalous (strange) transport processes are described by the general equation [8]:

r r 2 (t ) = 2 D gen + t µ , where

r r 2 (t )

(7)

is characteristic size of region, in which the particle visits (oxidant

molecule) to time moment t, Dgen is generalized transport coefficient. At 0≤µ<1 it is spoken on subdiffusive transport processes and at 1<µ≤2 – on superdiffusive processes. The value µ is connected with connectivity index θ of walk trajectory of oxidant molecule on polymer structure as follows [8]:

µ=

2 . 2+θ

(8)

The sign of connectivity index defines topology of oxidant molecules walk. Particles Z are traps or captures for the mentioned molecules, interrupting their trajectories owing to that polymer’s structure is divided into a number of “substructures” and oxidant molecule walk is only allowed within the limits of such “substructure” up to meeting with Z particle. This

The Theoretical Description of Modified Polyethylene Thermostability…

77

means violation of connectivity of walk trajectory [8] and index θ becomes negative. Then from the equation (8) follows the condition µ>1, i.e., is observed from subdiffusive transport process for initial HDPE, where the absence of Z particles assumes the oxidant molecule walk on the whole polymer’s structure (up to meeting with reactive center of macromolecule), up to superdiffusive regime for compositions HDPE+Z. It will be noted, that the discrepancy of temperatures T5%, calculated according to the equation (6) for rapid diffusion and experimental values T5% (∆T5%) increases at rise of contents Z CZ (Figure 1). In Figure 2 the dependence ∆T5% on CZ is shown, which is linearized by argument

C Z1 2

∆T5% = 90C Z1 2 ,

using and analytically is expressed as follows: (9)

where ∆T5% gives in K and CZ – in mass.%. The attention is drawn to the approaching tendency of experimental values T5% to the data, obtained in inert gas (helium) atmosphere, observed in a Figure 1. Using the theoretical curve 2 of this figure (rapid diffusion case) and the equation (9), the value CZ can be estimate, at which the value T5% for compositions HDPE+Z, obtained in air and in inert gas atmosphere, become equal, i.e., all oxidant molecules will be absorbed by Z particles. Such condition is realized at CZ≈3,5 mass.%. From the only geometric considerations using experimentally determined sizes of Z particles [9], can be calculated, that at the mentioned content Z a polymer structure will be divided into “substructures” with characteristic linear size ~4,5 mu, in which the oxidant molecule walk will be restricted, i.e., in the limits of “own” connectivity component [8].

Figure 2. The dependences of value of experimental and theoretical data TGA discrepancy ∆ T5% on Z contents CZ for compositions HDPE+Z.

78

A. Kh. Malamatov and G. V. Kozlov

CONCLUSIONS Therefore, the results of the present paper have shown the applicability of fractal model of anomalous diffusion for quantitative description of TGA data in case of compositions HDPE+Z. The influence of diffusion type on the value of sample 5%-th mass loss temperature is shown and was offered structural analysis of this effect. The critical content Z is determined, at which degradation will elapse so, as in inert gas atmosphere.

REFERENCES [1] [2] [3] [4] [5] [6]

[7]

[8] [9] [10] [11] [12] [13] [14]

Askadskii A.A. Structure and Properties of Thermostable Polymers. Moscow, Khimiya, 1981, 320 p. Korshak V.V. Chemical Constitution and Temperature Characteristics of Polymers. Moscow, Nauka, 1970, 419 p. Van Krevelen D. Properties and Chemical Constitution of Polymers. Moscow, Khimiya, 1976, 414 p. Sazanov Yu.N., Kudryavtsev V.V., Svetlichnyi V.M., Fedorova G.N., Antonova T.A., Aleksandrova E.P. Vysomolek. Soed. A, 1983, v. 25, №5, p. 975-978. Mikitaev A.K., Beriketov A.S., Korshak V.V., Taova A.Zh. Vysomolek. Soed. A, 1983, v. 25, №8, p. 1691-1696. Dolbin I.V., Kozlov G.V., Bazheva R.Ch., Shustov G.V. Mater. of V All-Russian nauchn.-tekhn. konf. “Novye Khimicheskie Tekhnologii: proizvodstvo I primenenie”. Penza, 2003, p. 42-45. Mashukov N.I., Serdyuk V.D., Kozlov G.V., Ovcharenko E.N., Gladyshev G.P., Vodachov A.B. Stabilization and Modification of Polyethylene by Oxygen Acceptors. (Preprint). Moscow, IkhF AN SSSR, 1990, 64 p. Zelenyi L.M., Milovanov A.V. Uspekhi Fizichesk. Nauk, 2004, v. 174, №8, p. 809-852. Kozlov G.V., Zaikov G.E. Structure of the Polymer Amorphous State. Utrecht-Boston, Brill Academic Publishers, 2004, 465 p. Kozlov G.V., Sanditov D.S. Anharmonic Effects and Physical-Mechanical Properties of Polymers. Novosibirsk, Nauka, 1994, 261 p. Shogenov V.Kh., Akhkubekov A.A., Akhkubekov R.A. Izvestiya VUZov, SeveroKavkazsk. region, estestv. nauki, 2004, №1, p. 46-50. Kozlov G.V., Dolbin I.V., Zaikov G.E. J. Appl. Polymer Sci., 2004, v. 94, №4, p. 13531356. Kozlov G.V., Temiraev K.B., Shustov G.B., Mashukov N.I. J. Appl. Polymer Sci., 2002, v. 85, №6, p. 1137-1140. Dolbin I.V., Burya A.I., Kozlov G.V. Fundamental. Issledov., 2005, №3, p. 39-41.

In: Chemical and Biochemical Physics: New Frontiers ISBN 1-60021-165-8 Editor: G. E. Zaikov, pp. 79-86 © 2006 Nova Science Publishers, Inc.

Chapter 10

QUANTUM-CHEMICAL CALCULATIONS OF ANALYSIS REACTIVITY S-AND O-ANNES, GENERATED FROM 6-METHYL-2-THIO-, 2-ALKYL(ARALKYL)THIOURACILS A. I. Rakhimov 1∗, E. S. Titova 2†, R. G. Fedunov 2, V. A. Babkin, G. E. Zaikov 1 2

Volgograd State Technical University, Volgograd; Russia Institute of Environmental Cemical Problems, Volgograd Moscow, N.M. Emanuel Institute of Biochemical Phisics

ABSTRACT The method ab-initio in basis 6-31G ** investigates electronic structure S-and O aniones, generated of 6-methyl-2-thio-, 2- thio-, 2-alkyl(aralkyl)thiouracils. Designed full electronic energy S-anion is higher, than O-anion on 55.9 кJ/mol. The carried out) calculations, and also kinetic researches of reaction SN2 of replacement of halogen in halogen substituted compaunds have proved high selectivity of reception S-mono -and S, O –aniones of 6-methyl-2-thiouracil.

AIMS AND BACKGROUNDS Derivatives of 6-methyl-2-thiouracil (I) are widely used, as medical products for treatment virus HSV-1 [1, 2], hyperfunctions of a thyroid gland [3], illnesses Huntington, Parkinson, migraines, depressions, infringements of memory [4]. Derivatives 2-thiouracil are inhibitors of human immunodeficiency virus revers transcriptase of type (HIV-1) and show powerful inhibitiones properties in attitude HIV-1 in vitro [5-18]. One of the most developed ∗

†

e-mail: [email protected] E – mail: [email protected]

80

A. I. Rakhimov, E. S. Titova, R. G. Fedunov et al.

methods of reception of connections on the basis of (I) is nucleofilic replacement of halogen in halogen substituted compaunds, proceeding with participation S-and O - aniones, generated of connection (I) [9 - 10].

METHODICAL PART For calculation of molecular models it was used quantum-chemical a method ab-initio (basis 6-31G **) from software package GAMESS version 6.0 [19]. Minimization of full energy of system was carried out градиентным by a method with optimization of all geometrical parameters at the "frozen" coordinate of reaction. Calculation was carried out in classical approach(approximation) of an isolated molecule, a gas phase.

RESULTS AND DISCUSSION

O -

O

N

NH Me

N

S-

Me

(II)

N H (III)

S

Full energy of anion (III) is higher, than anion (II) on 55.9 кJ/mol. In this connection formation of it with other things being equal is improbable. It proves to be true experimentally kinetic researches and synthesis extremely S-monosubstituted compaundes at generating anione (II) in water-dioxane environments at temperature 30 - 50 0С: reaction of Sreplacement, for example for ethylbromid, goes during 15 mines with 90 %-s' exit 2-ethyl-6methylpirimidin-4 (3Н)-one. Therefore the electronic structure of a transitive condition determining SN2 replacement of halogen in halogen substituted compaunds with participation aniona (II) is considered. In a case methylbromid and benzylbromid reaction goes on to the circuit 1. O NH Me

N

-

O S-

RBr

NH Me

N

H

H

S ------ C ------ Br R

R = H (IV a), R = C6H5 (IV b) The circuit 1

O NH -Br -

Me

N

SR

Quantum-Chemical Calculations of Analysis Reactivity S-and O-Annes…

81

Apparently from table 1, in process of approach aniona (II) to carbon atom methyl groups there is an increase of a negative charge at atom of bromine in a transitive condition (IV a). And on distance 0.24 nm in a barrier point ionization of bromine achieves -0.78, and then at the further rapproachement of atoms of carbon and sulfur on 0.22 nm bromine as an ion "leaves" a transitive condition. Simultaneously to ionization of bromine there is a formation covalenciv connections between atoms of sulfur and carbon methylbromid, that is accompanied by reduction of a negative charge by atom of sulfur. At once after a barrier point on distance 0.22 nm cooperating atoms С-S sharp reduction of a charge by atom of sulfur till0.14 is observed (a reference value of a charge-0.53), and further on distance 0.20 nm a charge on atom of sulfur becomes positive, and the bromine - ion practically leaves with a charge-0.96. Nucleofilic replacement as has shown calculation, goes with allocation of energy 16.3 кI/mol. Table 1. Change of charges on atom of bromine in methylbromid, atom of sulfur in anion (II), in the reaction proceeding under the circuit 1 №

Length of connection R, nm

C ----- S 1 1 2 3 4 5 6 7 8

2 0.300 0.280 0.260 0.240 0.220 0.200 0.190 0.182

C ----- Br 3 0.200 0.198 0.201 0.261 0.302 0.329 0.343 0.343

Charge

The order of connection P

qBr

qS

4 -0.32 -0.27 -0.30 -0.78 -0.92 -0.96 -0.96 -0.94

5 -0.53 -0.52 -0.51 -0.34 -0.14 0.02 0.10 0.26

C -----S

C -----Br

6 < 0.050 < 0.050 < 0.050 0.440 0.718 0.844 0.878 0.930

7 0.861 0.901 0.882 0.316 0.083 < 0.050 < 0.050 < 0.050

Table 2. Change of charges on atom of bromine in benzylbromid, atom of sulfur in anion (II), in the reaction proceeding under the circuit 1 №

Length of connection R, nm

C ----- S

1 1 2 3 4 5 6 7 8

2 0.300 0.280 0.260 0.240 0.220 0.200 0.190 0.183

C ----- Br

3 0.199 0.201 0.205 0.291 0.365 0.359 0.359 0.359

Charge

qBr

qS

4 -0.23 -0.25 -0.29 -0.87 -0.90 -0.90 -0.90 -0.90

5 -0.52 -0.51 -0.50 -0.27 0.00 0.18 0.23 0.26

The order of connection P

C ----- S

C ----- Br

6 < 0.050 < 0.050 < 0.050 0.528 0.877 0.900 0.919 0.928

7 0.920 0.907 0.878 0.142 < 0.050 < 0.050 < 0.050 < 0.050

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A. I. Rakhimov, E. S. Titova, R. G. Fedunov et al.

At transition from methylbromid to benzylbromid (table 2) ionization of connection carbon - halogen considerably grows as approaching electrofilic to the centre anion (II): the charge on atom of bromine is increased till-0.87 on distance 0.24 nm in the field of a barrier point. In too time as against methylbromid for benzylbromid in a transitive condition (IV b) near to a barrier point on distance 0.20 nm the charge on atom of sulfur is equal 0.18, that in 9 times more, than a transitive condition (IV a). Reaction benzylbromid with anion (II) is accompanied by a prize of energy equal 50.6 кJ/mol, that in 3 times it is more, than for methylbromid (rice 1). Results of quantum-chemical calculations will be coordinated to kinetic parameters of reaction SN2 of replacement (table 3). The constant of speed SN2 of replacement for ethylbromid (the nearest homolog of methylbromid) in 17 times is less at temperature 50 0С, than for benzylbromid (unambiguity SN2 of replacement for both halogenides is proved experimentally). Table 3. Kinetic parameters of SN2-replacement of bromine in ethyland benzylbromid by anion (II)

Temperatur e Т, 0С 30 40 50

Ethylbromid Constant of Energy of speed activation К, l /mol · с Еа, кJ/mol 0.0009 52.35 0.00178 0.0032

Benzilbromid Constant of Energy of activation speed Еа, кJ/mol К, l/mol·с 0.025 32.83 0.038 0.055

Table 4. Change of charges on atom of bromine methylbromid, atom of oxygen in anion (V a) in the reaction proceeding under the circuit 2 Length of connection R, nm №

1 1 2 3 4 5 6 7 8 9 10 11

C ----- O

2 0.300 0.280 0.260 0.240 0.220 0.200 0.180 0.170 0.160 0.150 0.143

C ----- B r

3 0.198 0.198 0.200 0.203 0.211 0.254 0.299 0.315 0.328 0.342 0.377

Charge qBr

qО

4 -0.29 -0.30 -0.32 -0.36 -0.44 -0.76 -0.92 -0.94 -0.96 -0.96 -0.96

5 -0.73 -0.73 -0.74 -0.75 -0.76 -0.77 -0.76 -0.74 -0.71 -0.68 -0.64

The order of connection P

C ----- O

6 < 0.050 < 0.050 < 0.050 < 0.050 0.053 0.239 0.465 0.545 0.605 0.664 0.724

C ----- B r

7 0.879 0.871 0.856 0.828 0.760 0.375 0.103 0.058 < 0.050 < 0.050 < 0.050

Quantum-Chemical Calculations of Analysis Reactivity S-and O-Annes…

83

The quantum-chemical method ab-initio investigates also reactionary ability O-aniones, generated of 6-methyl-2-thio-, 2- thio-, 2-alkyl(aralkyl)thiouracils (V a, V b) in reaction SN2 of replacement methyl- and benzylbromides, proceeding under the circuit 2. H H O ------ C ------ Br

ON Me

N

RBr SCH2R

R = H (V a), R = C6H5 (V b)

N Me

N

-

R SCH2R

OCH2R N -Br -

Me

N

SCH2R

R = H (VI a), R = C6H5 (VI b)

The circuit 2

Polarization of connection carbon bromine (tables 4, 5) in methylbromid goes to a lesser degree, than in benzylbromid at the approach anion (Vа) to electrofilic to the centre: for a condition (VI a) the charge on bromine is equal-0.76, and for (VI b) the charge is equal-0.84. The greater degree of ionization of bromine in (VI b) and his(its) leaving(care) as an ion the increase of a constant of speed of reaction for benzylbromid in 16 times speaks in comparison with ethylbromid (table 6). The order formed ковалентных connections С-S, С-О and разрываемых polar covalencive connections C-Br (table 1, 2, 4, 5) during course of reaction change differently at the first and second stages of process. At the first stage in a barrier point 0.24 nm there is a sharp amplification(strengthening) of connection С-S simultaneously to sharp easing connection C-Br, and on distance 0.20 nm connection C-Br is completely broken off and formed strong ковалентная connection С-S (table 1, 2). Less reactionary capable Oaniones (V a, V b) participate in formation(education) ковалентной connections, coming nearer on shorter distance to electrofilic centre 0.20 nm, and are characterized by slower increase about connection (table 4, 5) The thermodynamics of reaction benzylbromid with anion (V b) also develops in its advantage(benefit) - reaction goes with allocation of energy equal 51.4 кJ/mol, and is close to thermodynamics for benzylbromid and anion (II). The big reactionary ability anion (II) in comparison with anion (V b) speaks the smaller power barrier necessary for course of reaction and equal 51.9 кJ/mol, the size of a power barrier for anion (V b) makes 64 кJ/mol. It will be coordinated by that the constant of speed of reaction SN2 of replacement in benzylbromid with participation anion (V b) in 10 times is less, than a constant of speed SN2 of replacement for anion (II). Experimentally found energy of activation SN2 of replacement of bromine in methylbromid and benzylbromid by anion (II) and aniones (V a), (V b) (tables 3, 6) according to equation Аrrenius correlate with sizes of the power barriers designed by a method ab-initio ( rice 1). Reaction of O - replacement is energetically more favourable, than N-replacements (rice 2), that also will be coordinated to the experimental data proving formation(education) S, O – disubstituted in IR-spectrum there are no strips of absorption νС=О, characteristic for carbonil groups).

84

A. I. Rakhimov, E. S. Titova, R. G. Fedunov et al. Table 5. Change of charges on atom of bromine in benzylbromid, atom of oxygen in anion (V b) №

Length of connection R, nm

C ----- O

1 1 2 3 4 5 6 7 8 9 10 11 12

2 0.300 0.280 0.260 0.240 0.220 0.200 0.190 0.180 0.170 0.160 0.150 0.145

Charge qО qBr

C ----- Br

The order of connection P

C ----- O

3 0.198 0.199 0.201 0.205 0.216 0.280 0.364 0.368 0.373 0.377 0.381 0.383

4 -0.22 -0.24 -0.28 -0.33 -0.43 -0.84 -0.91 -0.91 -0.92 -0.92 -0.92 -0.92

5 -0.74 -0.75 -0.74 -0.74 -0.75 -0.76 -0.73 -0.72 -0.71 -0.69 -0.66 -0.64

6 < 0.050 < 0.050 < 0.050 < 0.050 < 0.050 0.278 0.448 0.516 0.576 0.629 0.680 0.707

C ----- Br

7 0.925 0.917 0.883 0.846 0.755 0.208 < 0.050 < 0.050 < 0.050 < 0.050 < 0.050 < 0.050

Table 6. Kinetic parameters of SN2-replacement of bromine in ethyland benzylbromid by anion (V a) and (V b) Ethylbromid Temperature Т, 0 С 30 40 50

Constant of speed К, l /mol · с 0.00032

Energy of activation Еа, кJ/mol -

Benzilbromid Energy of Constant of speed activation К, l /mol · с Еа, кJ/mol 0.0021 41.13 0.0038 0.0056

CONCLUSIONS Thus, quantum-chemical calculation with the help of a method ab-initio has allowed to clear the reason of high reactionary ability of aniona (II) and selectivity of reception S-monoand S-, O -di substituted connection (I). For reproduction of a barrier of reaction, the standard technique of minimization of energy of a geometrical structure from the previous calculation was used at new value of the fixed coordinate. The choice of basis is caused by presence in molecular system of elements of the third and fourth line of Mendeleev,s table, with strongly pronounced дальнодействующими interactions due to extended d-оrbitales which can be taken into account(discounted) at inclusion in basis polarizing an exhibitor (asterisks in a designation of basis). Accuracy of calculation of full energy is defined(determined) by size virial factor which makes ~2.005 for the systems including Br, and ~2.002 for other systems.

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85

Differences in absolute values energies the activation, found experimentally, and designed by a quantum-chemical method, speak first of all distinctions in properties of gas and liquid phases though the relative laws found by both methods, completely coincide.

-3383,1

-3383,11

Full energy Е, AU

2 -3383,12

1 -

-3383,13

-3383,14

-3383,15

-3383,16 0,32

0,28

0,24

0,2

0,16

0,12

Length of connction R, nm

1 – by oxygen; 2 – by nitrogen

-734,54

Full energy E, AU

-734,55

-734,56

-734,57

2 1

-734,58

-734,59

-734,6 0,33 0,31

0,29

0,27

0,25

0,23

0,21

Length of connection R, nm

1- methylbromid, 2 - benzylbromid

0,19

0,17

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REFERENCES [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19]

Abdel-Rahman Adel A.-H. // Afinidad. 1997. V.54. № 468. Р. 135. Rahman A.A.-H., Abdel Aal M.T. // Pharmazie. 1998. 53. № 6. Р. 377. Besada Amir, Tadros N.B., Gawargyious Y.A. Egypt. J. Pharm. Sci. 1989. 30. № 1. Р. 251. Adav Geo, Kolczewski Sabine, Mutel Vincent, Wichmann Jurden Derivatives of 5Нthiazolo[3,2-а]-pyrimidina. Pat 0891978 (1998). USA, 1999. Maccha Marko, Antonell Guido, Balsamo Aldo, et. al. Farmaco(Amsterdam). 1999.V.54, №4. P. 242. Larson Janus S., Abdel Abl Mohammed Taha, et. al. J. Heterocycl. Chem. 2001. V. 38. №3. P. 679. Morris Joel, Adams Wade, Friis Janice, Wishka Donn. Pat 6124306 (1999). США, 2000. Mai A., Sbardella G., Artico M., et. al. J. Med. Chem. 2001. V. 44. №16. P. 2544. Mai A., Sbardella G., Artico M., et. al. Med. Chem. 1999. V.42. №4. P. 619. Quaglia M., Mai A., Artico M., et. al. Chirality. 2001. V.13. P.75. Sudbeck E.A., Mao C., Venkatachalam T.K., et. al. Antimicrob. Agents Chemother. 1998. V.42. №12. P.3225. Jmam Dalia R., El-Barbary Ahmed A., Nielsen Claus, et. al. Monatsh. Chem. 133. № 5. Р. 723. Ole S. Pedersen, Lene Petersen, Malene Brandt, et. al. Monatsh. Chem. 130. 1999. Р. 1499. Mitsuya, H., Broder. S. Nature. 325. 1987. Р. 773. Goff, S.P. J. Acquired Immune Defic. Syndr. № 3. 1990. Р. 817. Vorbruggen H., Bennua B. A. Chem Ber. 114. 1981. Р. 1279. De Clercq E. J. Med. Chem. 38. 1995. Р. 2491. Baba M., Tanaka H., Miysaka T., et. al. Nucleosides Nucleotides. 14. 1995. Р. 497. Schmidt M.W., Baldridge K.K., Boatz J.A., et. al. J.Comput.Chem. 1993, 14, 1347.

In: Chemical and Biochemical Physics: New Frontiers ISBN 1-60021-165-8 Editor: G. E. Zaikov, pp. 87-111 © 2006 Nova Science Publishers, Inc.

Chapter 11

MATHEMATICAL MODELS OF TUMOR PROCESSES AND STRATEGIES OF CHEMOTHERAPY Yu. A. Ershov and V. V. Kotin N.E. Bauman's Moscow State Technical University, Moscow, Russia

INTRODUCTION The particularities of cell population growth in general case are determined by the character of development of its individuals. Consecution of stages of cell growth formulated in the form of quasi-chemical equations represents branched chain reaction [1-4]. This fact allows quantitative description of influence of chemical agents on growth of cell populations, in particular tumor ones basing on mathematical apparatus of chain processes kinetics [5]. In work [2] on the base of earlier obtained kinetic equations of cell growth the mathematical models for calculation of effect of individual chemical substances and their mixtures on tumor growth were developed. These ratios allow quantitative estimating of synergism effects and toxicants antagonism, calculating of their critical concentrations and other toxicometric characteristics. Suggesting kinetic theory allows establishing of general regularities of tumor growth, revealing of its mechanism and developing of objective criteria of estimation of activity of carcinogenic and antitumoral substances. Professor N.M. Emanuel was one of the first who understood comprehensive facilities of chemical kinetics methods, especially kinetics of chain reactions in investigation of biologic processes. In seventies of the last century he established the chemical-biological department in the Institute if Chemical Physics of USSR AS and didn’t grudge the time for explaining for us − young scientists how important and perspective the questions of biological kinetics were. Results of investigations of department of oncology were summarized in monograph [6]. The given work as well as a lot of others in essence grew from Nikolai Emanuel's ideas and works.

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MATHEMATICAL MODELLING OF CHEMOTHERAPY OF TUMORS During decades the introduction of preparations accompanying by increase of relapsefree survivability with tumors is characteristic for oncology. These medicines allow conducting of surgical treatment and also increasing intensity and duration of medical procedures at localized and metastatic tumors. However the long-term work doesn't lead to essential increase of total survivability of patients. The search of optimal scheme of cytostatics application is the most complex. Experience shows that it is possible to find the optimal solution only at careful analysis of growth of intact tumors which is determined by particularities of growth kinetics. Multiformity of tumor pathologies and consequently of regimes of malignant cells growth cause the broad sphere of action for investigation of experimental tumors. However, modelling of tumors by grafting of pathogenic cells to laboratory animals is accompanied by known difficulties connected with long process of studies, incommensurability of experiments conditions and obtained results. General mathematical description of various sicknesses allows approaching from general positions to problems of processing and interpretation of clinico-laboratory and experimental database. Data analysis is realized with the help of mathematical model on the base of theoretical investigations. Initial database as a rule was got on animals' and plants' cells. Experimental tumor models which are directed on search of effective antitumoral effects became the main objects of pre-clinic investigations. Extensive material on biology of transplantable, induced and spontaneous malignant tumors of animals is accumulated in experimental oncology at present [6]. This gives the possibility of using of presenting material for quantitative analysis and summarizing of data, establishing of general regularities of development of tumor processes and revealing of quantitative criteria characterizing tumor growth. Knowledge of kinetics of tumor development under the influence of chemical agents allows playing over a great number of regimes of medical influence in the framework of mathematical calculation experiment. As a result we may mark out and determine the direction of in vivo experiments discarding knowingly unfavorable outcomes. Additional introducing of tumors of episodical members into growth kinetics model opens possibility of probabilistic estimation of development of pathogenic population since it reflects carcinogenesis processes more accurately. In experimental data for macro-scopic description of the process of tumor growth one uses the following variables: m(t) − mass of affected part of bio-tissue and also geometrical parameters − tumor volume V(t), square of affected surface S(t), characteristic linear size of tumor, for example average diameter D(t) of affected section having the form of round spot on skin surface. One assume that all listed variables m(t), V(t), S(t), D(t) integrally characterize the tumor growth and are in proportion to the number of tumor sells − the main phase variable appearing in models of tumor growth. Such proportionality is then used for comparison of theoretical and experimental data. For describing of dynamics of tumor growth during several decades a lot of models were proposed [6, 25]. Only some of them are interesting until now. The problem is that intact

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tumor growth remains poorly studied. So, a lot of models are hypothetical. At the same time, they help in understanding of regularities of tumors developing and medical substance action. As a result the real possibilities of medical treatment effectiveness increase are opened. It is advisable to present examples of description and mathematical modelling of various types of cancerous growth as illustrations. The most interesting models of tumor growth at chemical agents effecting are models of Skipper-Schobel-Wilcox, Delbruck-Luria, GoldieColdman, Speer-Retsky, and Norton-Simon [6]. One of the first kinetic models was formulated by Skipper et. al. (Skipper-SchabelWilcox) [7] on the base of data of observation for mousse with leucaemia L1210. the growth of this tumor may be described by exponential law: F= Foert, where F − the value characterizing the current size of tumor; F0 − initial value of F; r − Mal'tus's parameter of growth characterizing the given type of tumor until it will reach lethal volume equal to 109 of cells and equivalent to 1cm3. About 90% of leucemic cells are divided each 12-13 hours (r = 0,8 h-1). As a consequence of constancy of part of dividing cells or so-called "part of growth" the time of doubling is always constant. Considerable tumors in methodological relation are very suitable for experimental kinetic studies. These models assume life-time measuring of sizes of tumors in both control experiments and under various effects including chemotherapeutical. Moreover, considerable tumors in many cases give metastases. From this point of view it is interesting to study the Walker carcinosarcoma, Luise carcinoma and some melanomas. Considerable tumors are also suitable for modelling of surgical medical treatments and studying of regularities of recidivations development in those cases when operative removal of tumors is not radical. Walker carcinosarcoma was obtained in 1928 from spontaneously appeared carcinoma of mammary gland [6]. It is interweaved with rats of various lines, grows infiltratively, gives metastases to lymph nodes and lungs. It was studied by Shrek [8] for the first time, he applied the linear dependence for describing of tumor growth:

D = b(t − t 0 ) ,

(1)

where D − average diameter of tumor, b − rate of growth, t0 − the point of intersection of line with time axis (latent or lag period). The Gompertz' equation is often used for description of tumors growth kinetics: F = Fo exp(a(1-e-bt)),

(2)

where F − the value characterizing the current size of tumor; F0 − initial value of F; a, b − parameters of growth characterizing given type of tumor. In other cases the kinetics of tumors growth is described by equation of auto-catalysis (in biology it is logistic Verhulst' equation):

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Yu. A. Ershov and V. V. Kotin F= F∞/(1+(( F∞ - Fo )/ Fo)exp(c(1-e-pt),

(3)

where F − the value characterizing the current size of tumor; F0, F∞ − initial and limited values of F; c, p − parameters of growth characterizing the given type of tumor. F∞ = p / a, where p − factor of chain continuation, a − factor of auto-inhibition. For example for Walker carcinosarcoma the data on growth of tumor volume V are well described by Gompertz' equation:

V = 3,9 ⋅ 10 −6 e17.1(1−e

−0.21 t

) , cm3.

(4)

It is obvious from numerical parameters that tumor volume asymptotically approaches the value V∞ = 3,9·10-6е17,1 = 104 cm3. An important distinction of Gompertz' kinetics from exponential growth is the fact that the part of growing cells in the first case is not constant but it is decreased in time exponentially. In Gompertz' model if patient has a large part of tumor mass the part of growing cells will be not large, so the number of annihilable cells will also be limited. Moreover, efficiency of chemotherapy will depend on the fact at which section of Gompertz' curve the tumor is in the case of given patient. According to data of another works the kinetic curve of tumor diameter D change is described by auto-catalytic equation:

D=

5,5 , cm 1 + 18,2e −0,18t

(5)

The limited volume of tumor calculated by the value D∞ = 5,5 сm is equal to 87cm3, i.e. is by 15% lower than previous value V∞. In accordance with other works' data kinetics of tumor mass change may be described by auto-catalytic equation:

m=

123.2 ,g 1 + 513e −0, 27 t

(6)

with limited size of tumor close to values obtained in previous cases. Heterogeneity of growth rate of tumors of both one and various types was established. And: • • •

Tumors having high rate of growth with doubling time 30 days (chorioncarcinoma) are characterized by high sensitivity to medical treatment; Tumors with doubling time more than 60 days (epidermoid cancer of head and neck) have less sensitivity of chemiotherapy; Tumors with doubling time more than 90 days (cancer of colon) have low sensitivity to cytostatic agents).

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Doubling time may be short in the case of large part of cells with low frequency of spontaneous cells dissipations. But it is not necessarily so that the long doubling time means low proliferative activity. Tumors with high frequencies of cells dissipations have lower rate of growth than tumors with analogous proliferative activity and less cells dissipations. High proliferative activity and high frequency of cels dissipations mean large number of mitosises per unit time. The strain of adenocarcinoma 755 was obtained from spontaneous appeared tumor of mouse of low-cancerous line C57 [9]. The tumor has structure of alveolar adenocarcinoma and in some cases has metastases to lungs. The growth of adenocarcinoma 755 of mouses of line C57B1 is described by the dependence:

Vr = 2 t (K −K1Vr ) , in which K = 0,27 days-1 and K1 = 0,0014 days-1, Vr = Vt/V0; V0 – volume of inoculum. Disadvantage of this equation is false identification of inoculum volume with initial volume of tumor. Moreover, limited relative volume of tumor more than in three times exceeds the maximum relative volume observing experimentally. Application of autocatalysis equation [11] of the form:

Vr =

75.5 1 + 74,5e −0.53t

gives more realistic value of V∞ / V0. Rate constants of tumor growth are something differed in dependence on animal sex and inoculum age. Some discrepancies in rates of adenocarcinoma 755 growth may be explained by influence of type, size and age of inoculum, method and place of inoculation, sex and line of animal, and also by accuracy degree of estimation of parameters and selection of approximation formulas [6]. Skipper-Schobel-Wilcox model is based on two important presumptions: exponential growth and homogeneous sensitivity to chemotherapy. Model should not "work" effectively if some cells in tumor are biochemically refractorious to applied dozes of cytostatic agents. If such cells exist, then even in the case of elimination of all sensitive cells by definite duration of medical treatment the further therapy by the same scheme wouldn't help. There were some attempts to apply this model for substantiation of accessory (adjuvant) therapy of micro-metastases in the cases of considerable tumors. It is known that micrometastases contain significantly larger amount of dividing cells in comparison with considerable metastases. Due to this reason if chemotherapy erases predominantly dividing cells, then the part of killed cells in micro-metastasis should be larger. However clinical investigations didn't confirm these suppositions. Authors of model considered possibility of gaining of such resistance by means of accidental mutations in the course of process of natural growth history. In this case the only way which may guarantee the absence of resistant cells appearing is starting the therapy at that moment when tumor is so small that it had no time for such mutations. Conceptions of development of medical resistance are originated in investigations by Delbruck and Luria. They found that various cultures of one bacterial line possess various

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frequencies of appearing of resistance to bacteriophages and resistance is developed on accidental base at various times after exposition of virus. Tumors which acquire resistance to cytostatic agents already before the first exposition of preparations were found in medical practice. It is obvious that in this case we may reach elimination of tumor cells only by application of cytostatic agents combination (polychemotherapy) since probability of acquiring of resistance simultaneously to several cytostatic agents is low. Goldie and Coldman suggested the following equation ss mathematical model of frequency of resistance occurrence:

P(N ) = exp{− x(N − 1)} where P(N) − probability of mutations absence, x − frequency of mutations, N − number of cells in tumor. If frequency of mutations is equal to x = 10-6 the probability of mutations absence at cells number N = 105 is equal to 0,905, at cells number N = 107 is 0,000045. Due to this reason increase of cell mass by two orders (from 105 up to 107) may transform tumor from curable into incurable. According to Goldie-Coldman model the tumor growing from one malignant cell has at least 90% probability of recovery at cells number 105 but zero probability at cells number 107. In this case, even at the condition of favourable ratio between cells and stroma the tumor larger than 1cm3 will always be incurable if carrying out therapy by one cytostatic agent. That is why the best strategy of cancer chemotherapy is medical treatment at minimum tumor size before the cells will acquire resistance and ability to metastasis. Correspondingly, if the treatment was started then maximum number of effective preparations should be applied as soon as possible. The main problem at that is prevention of development of cells resistance to a lot of cytostatic agents in the case of acquiring of such ability in relation to one of them. This recommendation corresponds to principles underlying combined chemotherapy. As it was mentioned above, one of the permissions of given hypothesis is homogeneous sensitivity and absolute medical resistance. Clinical experience testifies to the contrary situation. Cancerous tumors which begin to grow after realization of one or another scheme of chemotherapy usually are not completely resistant to this scheme in the case of its repeated application. Because of this reason we can't consider that all cases of chemotherapy inefficiency are caused by absolute medical resistance. There are two explanations of this phenomenon. Firstly, some tumors don't die as a result of chemotherapy because of temporary absolute medical resistance which then is reversed. Secondly, sensitive cells due to some reasons are erased not completely by preparation to which they are still sensitive. Recurrentness of tumor process also essentially depends on the form of growth curve which as they often assume has exponential form. However, as the analysis pf database shows the exponential growth of considerable tumors is most likely the exception, than the rule. One of the variants of non-exponential growth is the growth in accordance with Gompertz kineitcs. Time of doubling is increased constantly with tumor growth and this fact means that tumor while progressing grows slower. Deceleration to a greater extent may be the consequence of increase of number of cells losses.

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Tumors growing in accordance with Gomperts kinetics in the presence of sensitivity to cytostatic agent should reply on carrying out treatment in special way. The reason is in special "behavior" of micro-metastases residuary after surgical removal of primary tumor. In them the part of growing cells will be larger and so in spite of small number of killed cells their proportion will be larger than in the case of clinically determined sizes. Analysis of clinical data from various investigations of adjuvant therapy shows that in many cases curves of tumors growth are described by Gompertz model. Gomperts kinetics is the feature of effective homeo-static system: at the size close to plato the growth is decelerated and tumor becomes resistant to cytostatic agents, but in the case of size decrease the growth is restarted and it reach previous size fast. As a consequence, the tumors growing in accordance with Gomperts kinetics are hardly totally eliminated out of organism. In spite of the fact that the time from surgery to relapse is longer in the case of carrying out of adjuvant therapy the time from surgery to death is equal in both cases. The large part of cells depressed by adjuvant therapy is balanced by accelerated growth of relapsing cells after therapy carrying out. Another approach is the using of preparations combination not possessing cross resistance. In accordance with "the rule of the worst preparation" the therapy by less effective preparation should be used either as the first or as the second but for a longer time. From the other hand, efficiency of medical treatment of considerable tumors may be increased by depressing of growing clones at the beginning and then by maximum effect on numerically less slowly grown clones. Thus, on the base of mathematical modelling one may create methods which are able to improve relapse-free and total probability of survival. The problem is in the development of technique of their optimal application. Analysis of spacious database on dynamics of tumor growth and its models shows that applied mathematical models (see above) are in essence empirical curves of regression (approximation formulas) [6]. Such curves represent imitational models with one or another accuracy describing experiment results. At that parameters of regression curves as a rule don't have definite biological meaning and are not clearly connected with mechanism of cellular growth. In connection with all said above there is a problem of development of models based on the mechanism of cellular populations growth in general case and tumor cells in particular. Ecotoxicological model may be related to such models [1-4].

2. ECOTOXICOLOGICAL MODEL OF CELL GROWTH Dynamics of development of biological populations in general case and cells populations in particular may be formally described by various empirical equations. For various biological forms logistic Verhulst dependence [12, 13] is the most general: N (t) = (p/a) / (1 + (p/a/ N0 -1) exp (-pt)),

(7)

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Yu. A. Ershov and V. V. Kotin

where N(t) − current size of population at moment t, N0 − initial size of population at t = 0, p − growth factor, a − auto-inhibition factor (kinetic coefficients). Verhulst function is widely used. One of the reasons of such popularity in addition to its community is the evidence of differential kinetic law of growth: dN/dt = pN - aN2, N = N0 at t = 0.

(8)

Here kinetic coefficients p and a are the same as in equation (7). Formula (7) is the particular integral of differential equation (8). Verhulst model contains two parameters − p and a. Moreover, the equation contains initial size of population N0. Equation (8) undoubtedly is identical to corresponding Semenov's equation which describes kinetics of N active sites in branched chain reaction with quadratic law of chain termination and zero order of initiation [5]. However the essence of processes is different. Requirement of development of model based on more detailed mechanism of growth is caused by discrepancy between calculated by equation (7) and numerous experimental data. At the initial moment of exponential growth experimental size of population and calculated one by equation (7) are often significantly differed. The difference may be equal to several orders by value. Although during the period of growth deceleration theoretical curve corresponds to experimental data. Curves of cells of Saccharomyces cerevisiae yeast growth in suspension at various concentrations of nickel (II) sulfate may serve as an example (Figure 1) [14]. These curves are the evidence of toxic action of nickel (II) ions. Increase of toxicant concentration leads to decrease of rate during the period of exponential growth (parameter p in equation (7)) and maximum size of population of yeast (Parameter p/a in equation(7)) at one and the same initial size of yeast population, N0=100 cells/ml. Analogous data were received in [14, 15] under studying of toxic action of silver (I), copper (II), chromium (I), chromium (VI) and magnesium (II) salts and their combinations.

Figure 1. Cellular cycle.

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For nickel (II) at concentrations lower than 10 mmole/l toxic action was not found at the level of method sensitivity (cytoneutrality), in concentrations diapason 0,1−1,0 mmole/l poison revealed cytostatic effect. At concentrations higher than 2 mmole/l ions of nickel (II) rendered cytocide action on yeast. In none of listed cases equation (7) describes the growth of size of yeast populations in the whole time interval from inoculation up to reaching of maximum value. Calculated points of inflection on growth curves are also significantly differed from experimental points. Such discrepancy is observed in many other cases [12, 13] as well as in cases of tumors growth considered above. Obviously, mathematical model of growth (8) is a very rough approximation. It may be used for rough estimation, for example for classification of population development [16, 17] and also for description of experimental data on separate sections of growth curves. For creation of more adequate models more detailed description of individuals development and reproduction based on conceptions of biology of development is necessary. Quasi-chemical ecotoxicological model of cell growth is described in works [1-4]. Cell cycle (Figure 1) consists of two periods − inter-phase and mitosis. Mitosis (M-phase) includes separation of preliminary doubled nuclear material, nuclear fission and cell division − cytokinesys. Mitosis proceeds for about an hour. Inter-phase occupies significantly longer period between two mitosises including growth stage G1, phase of DNA (S) synthesis and phase of preparing to dividing G2. There is special control point of cell cycle (Start) at which growth (G1-phase) is finished and DNA synthesis is started. While passing the cycle cell increases its content and is divided into two or more young cells. In mammal's organism for supporting of life the millions of novel cells are produced secondly. The model of cell cycle beginning from mitosis-division of maternal cell may be presented as a chain of consecutive stages-periods: C1 Æ C2 Æ C3 Æ Cm Æ f C1

(9)

Here C1 is the young cell directly after division (stage of cycle G1), C2, C3, Cm are its further development phases up to mitoses (stages of cycle S, G2, M). Phases C1-Cm represent cells of four ages. In general case cells in culture are different and grow anisochronously. Quantitative characteristics of phases presented in literature are usually average statistical indexes which are measured on a large group of cells. That is why in general case for more accurate reflecting of population growth the chain (9) one should present as a large number of units.

2.1. Quasi-Chemical Description Of Population Growth In Medium of Substrates And Toxicants The requirement of growth of populations of one or another biological type is the presence of set of Ms nutritive materials (substrates) for given biological type S: Ms = (Ms1, Ms2, ... , Mse)

(10)

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where Ms − vector of substrates set (Ms1, Mse) for biological type S. Population is developed as a result of substrates assimilation. This process is reflected by the system of consecutive pseudo-chemical reactions in the following way (for short imaging index s is omitted): C1+(M1,Me) →C2 p11 C2+(M1,Me) →C3 p21 (11) Cn+(M1,Me)→fC1 pne (b) Here C1 is newborn individual which as a result of substrate M1 absorption is transformed into C2. Individual C2 absorbs M2 and is transformed into C3, and so on. In this way the whole chain of developing from newborn С1 to mature individual Cn is described. The set of kinetic constants (p11, pne ) determines the kinetic vector of growth. In general case of open systems one should take into account increase (or decrease) of quantity of population as a result of influx (outflow) from environment EE: EЕ ↔ C1 w1 EЕ ↔ C2 w2 -------EЕ ↔ Cn wn

(12)

where (w1-wn) − the set of rates of increase of individuals number С1 ... Сn from environment. Action of various toxicants (biologically active substances) Xi may be revealed at any stage of growth and is described in similar way: C1+X1→ C1X1 d11 C2+X2→ C2X1 d12 (13) Cn+Xt→ CnXt dnt (X1,Xt)→ EE rx1,rxt Here (X1,Xt) − the vector (list) of toxicants; {dij} − corresponding matrix of kinetic coefficients of toxic action. Moreover, one should take into account processes of auto-inhibition when for example mature individuals Cn hinder growth of young ones: Ci+C1→Ca1+Ci ai1 Ci+C2→Ca2+Ci ai2 (14) Ci+Cm→Cam+Ci aim Totality of these interactions is described by kinetic vector of auto-inhibition (ai1, aim). Sexual reproduction may be reflected in similar way.

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Natural mortality is considered by "monomolecular" reactions: C1→Cd g1 C2 →Cd g2 (15) Cn→Cd gn where (g1, gn) – multitude of coefficients of natural mortality. The system of pseudo-chemical reactions of population growth (11)−(15) with the help of kinetic coefficients is described in standard form [18-22] by systems of differential kinetic equations. As a result one obtains the system of high order, it is hard to carry out its qualitative analysis but numerical solution of such system due to modern level of computers is possible.

3. REDUCED TWO-STAGE MODEL OF POPULATION GROWTH 3.1. Quasi-Chemical Description And Mathematical Model Of Growth Let consider model of dynamics of populations in the view of shortened chain (9) of twostages − growth and division in the presence of two toxicants (inhibitors of growth) X1 and X2: C1 + M1 Æ Cm p Cm + M2 Æ f C1 b C1 Æ Cd g C1 + Cm Æ Ca + C1 a C1 + X1 Æ CX11 d11 C1 + X2 Æ CX12 d12 Cm + X1 Æ CX21 d21 Cm + X2 Æ CX22 d22

(16)

Here C1 − new-born individual which as a result of substrates absorption (М1, Mе) is transformed into individual C1, then C2 absorbing substrates is transformed into C3 and so on; matures individuals Cm with coefficient of reproduction f form f new individuals C1; (a, b, g, p, dij) − the set of kinetic coefficients determining growth of population. Increase (or decrease) of number of population as a result of in-flow (out-flow) from environment EE of substrates and individuals of various ages is taken into account by following pseudo-chemical equations of reactions: C1 Æ EE w1 Cm Æ EE w2 M1 Æ EE r1 M2 Æ EE r2 Here wi , ri – corresponding rates of in-flow (out-flow) of individuals.

(17)

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3.2. Mathematical Description of Quasi-Chemical Model of Growth Assuming that content of substrates M1, М2 and biologically active substances are constant the kinetics of chain growth and inhibition of population consisting of individuals C1 and Cm is described by the system of two differential equations: dc1/dt = -px c1 + f b cm + w1 dcm/dt = p c1 - bx cm - a c1 cm

(18.1) (18.2)

Here c1, cm − the numbers of growing and mature individuals, w1 − power of outside origin of individuals C1; a, b, g, p − kinetic coefficients of auto-inhibition, birth (branching), destruction and growth of population chain, рx=р+g. Constant amounts of substrates M1 and М2 are included into coefficients p and b, f − is coefficient of reproduction. For divided kariomitotic cell the value is f = 2. In general case it may be as higher, so lower than 2. Coefficients bx and px are functions of concentrations of inhibitors х1 and x2. px=p+g+d1; bx = b + d2

(19)

where d1 = d11 x1 + d12 x2; d2 = d21 x1 + d22 x2. The system of equations (18) for isolated population (w1=0) has two stationary points (0,0) and (c1'',cm''): c1''=(fbp-bxpx)/apx , cm''=pxc1''/fb

(20)

The first point (0, 0) marks total dying out of population. The limited number of population corresponds to the second point (c1' + cm''). In accordance with formulas (20) at conditions of isolation of population number in the whole and cells in various phases of development are functions of inhibitors content in medium. As it is obvious from ratios (19) with the rise of inhibitors Х1 and Х2 contents the values bx and px are increased. At that the limited number of С1 and С2 is decreased and reaches zero if the equality is fulfilled: fbp-bxpx=0

(21)

The sets of concentrations (х1, х2) of inhibitors that are in agree with equation (21) are critical and represent multitude reflected on plane (x, y) as a line which may be called as critical curve of cytoside action of toxicants combination (X1, X2). In quasi-stationary approximation by Cm system (7) comes to one equation: dc1/dt=p1c1(K1 –c1)/(K2+ c1) + w1 Here are the notations are introduced:

( 22)

K1 =c1``=(f b p - px bx)/(a px); K2=bx/a

(23)

where K1 − limited specific number of individuals C1 at w1 = 0.

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In the absence of inhibitor at w1=0 solving the equation (9) by c1 one obtains direct relation of development of population of "cell type" (f=2) on time: c1( t ) = K ( 1 + H( t ) – ( H( t ) * ( 2 + H( t ) ) ) 1 / 2

(24)

where H( t ) = 0.5 Q0 exp( -p t )/K, Q0 = ( K – с0 )2 / с0. At values f ≠ 2 and g ≠ 0 the dynamics of population number c1(t) as rule couldn't be reflected in the form of simple analytic function on time. So, it is advisable to use reverse function t(c1): t(c1) = ln( (c1/c0)((K1 – c0)/(K1 – c1)) (1 + n) )/(n px )

(25)

where n = K1/K2. Graph of function (25) describes the growth of biological populations under the action of biologically active chemical agents in the absence of outside origins. It is advisable to call this dependence as ecotoxicological curve of population growth. Experimental data and graphs of function (25) (inverted coordinates) describing growth of yeast in the presence of chromium and nickel salts are presented in Figure 2 [14]. In the limits of measurements accuracy the calculated curves are in good agreement with experimental data under change of number approximately by six orders.

Figure 2. experimental points and graphs of function (25) describing growth of yeast in the presence of chromium (a) and nickel (b) salts [14]: a = 1,25⋅10-8 ml/h, b = 0,8h-1, р = 0,32 h-1, f = 2. Concentrations of salts (1) 0,0, (2) 0,5, (3) 0,8, (4) 1,0 and (5) 5,0 mmole/l; c – cells concentration.

PARAMETRITIC IDENTIFICATION OF ECOTOXICOLOGICAL MODEL BY EXPERIMENTAL KINETIC DEPENDENCES Mathematical model should take into account only those factors which determine dynamics of investigated process and allow explanation of mechanism of studied phenomenon. At that model will qualitatively correctly describe its main regularities.

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However kind of solutions depends on parameters of model and initial conditions. That is why while studying the processes proceeding in real systems by methods of mathematical modelling the problems of parametrical identification, i.e. problems of model's parameters determination by observations data are appeared. In the frame work of mathematical model by selection of parameters one may obtain solutions interpretive as transition from pathological into healthy state of organism. To have an opportunity for realization of such transitions in modeled system one should know how one or another preparation influence on real parameters. Knowledge of these characteristics allows speaking about statement of problem of optimal control of medical treatment that is the target of application of mathematical models in this region of investigations. According with literature data [6] we may determine (identify) parameters of ecotoxicological model for growth of various tumors. Reduced two-stage ecotoxicological model of population dynamics (22) in the absence of inhibitors and external flow of cells mass is described by the following equation:

b a−c dc , =c pb a + c dt

(26)

where c − number of growing cells; a, b, p – kinetic coefficients of auto-inhibition, branching and growth of population chain correspondingly. This equation may be summarized by any type of variable x quantitatively characterizing tumor growth proportional to c. Let get the equation (5) as experimental model of Walker carcinosarcoma. Parameters of this model are determined in the experiment. In general view this model is as follows: D(t ) =

D∞ D∞ − D0 − rt 1+ e D0

(27)

where D0 − initial size of tumor, D0 = 0,28cm; r − rate of population growth, r = 0,18cm/day; D∞ – limited capacity of medium for given type of tumor population, D∞ = 5,5cm. Derivative of the right part of (27) describes rate of change of tumor diameter D. This rate at corresponding moments of time should be equal to rate determined by equation (26). There is a set of experimental data for equation (27) in accordance to which it was obtained. These are the values x = (x0, x1, …, xN-1)T of tumor diameter measured at time moments t = (t0, t1, …, tN-1)T. So, me way write the equality substituting concentration values с= xi at moment t= ti:

dD dt

t=ti

= xi

b a − xi + εi , pb a + x i

(28)

where εi – some error at indefinite coefficients. In accordance with least-squares method the error functional minimization of which will give the best estimations of model parameters has the following form:

Mathematical Models of Tumor Processes and Strategies of Chemotherapy

 dD φ = ∑ w i  i=0  dt N −1

t=ti

b a − xi − xi pb a + x i

  

101

2

(29)

For obtaining of the minimum (29) we may use methods from theory of non-linear optimization, for example methods of Gauss-Zaidel or Markuardt [23]. We may assume that weights wi = 1. As a result of such optimization the following values of parameters were obtained: medium capacity b/a = 5,075; rate of population chain growth p = 0,25. Derivative from right part of (27) with values of (26) plotted on it under substitution into it of experimental data is presented in Figure 3.

dD dt dc dt c = xi t =ti

t

Figure 3. Comparison of growth rates for experimental (points) and desired ecotoxicological (line) models of carcinoma.

After integrating of (26) at c(t = t0) = D0 we obtain solution of ecotoxicological model corresponding to experimental data (Figure 4):

c(t) xi+1 xi

t Figure 4. The curve of number growth of carcinoma cells population calculated by ecotoxicological model.

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The described method allows identification of the model given by differential equation. Complexity of the problem is in the fact that possessing analytical solution (26) one may receive parameters of model determining its solution in accordance with least-squares method closely to experimental data. Such approach opens possibilities of reception of parameters estimation also for more complex dependences. Alternative approach to determination of parameters of model (26) is its comparison with anther model given also by differential equation but which solution is possible to obtain analytically. As an example we may present logistic model of growth (8), where F = N – current value of population number; r − Malthusian parameter; F∞ = N ∞ – capacity of medium (limited value of N). Solution of equation (8) with consideration of initial conditions Fo = N(t = 0) = N0, p – Malthusian parameter; F∞ = N ∞ – capacity of medium (limited value of N) is as follows: N( t ) =

K . K − N 0 − pt 1+ e N0

(30)

This solution is analogous to equation (27). So, we may form equality analogous to (28) by substituting instead of left part the expression (8) with substitution into it of parameters of experimental model (5):

 b a − xi x  + εi . x i r 1 − i  = x i pb a + x i D∞  

(31)

Functional reflecting sum quadratic error in equation (31) is formed in the same way as (29):

2

  x  b a − xi  φ = ∑  x i r 1 − i  − x i  . D∞  pb a + x i  i=0   N −1

(32)

Numerical search of minimum φ in space of parameters gives the following results: b/a = 6,078; p = 0,229. Geren carcinoma's strain was obtained in 1934 from spontaneous adenocarcinoma of rats uterus. It was transplanted on outbred animals. Transplantation is varied from 50 up to 90%; spontaneous resorption is usually not observed. In separate cases it metastasizes into regional and distant lymph nodes. Change of diameter of Geren carcinoma is described by equation of auto-catalysis [6]:

D=

3.9 , cm 1 + 48e − 0.3 t

(33)

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The average volume of tumors V was calculated from these experimental data. It turned out that its kinetics is described by degree expression V = 2,3·10-6t5.3, cm3. Under decrease of inoculum in two times the curve of diameters change and curve of corresponding volumes are described by degree equations:

D = 6,2 ⋅ 10 −3 t 2 , сm; V = 1,3 ⋅ 10 − 7 t 6 , сm 3 .

(34)

it is important to note that at various parts of kinetic curve experimental data may be satisfactorily approximated by functions of various types. Let take as initial experimental model the expression (33) in which the following values are determined: initial and limited values of tumor diameter D0 = 0,08 сm, D∞ = 3,9 compound and rate of tumor growth r = 0,3 сm/day. Parameters of ecotoxicological model are determined analogously by functional (29) minimization. As a result the following values of parameters were found: b/a = 4,532; p = 0,278. Dependence of growth rate of experimental model on time and also the values of ecotoxicological model given by differential equation (26) under substitution of experimental data to it and found by coefficients optimization are presented in Figure 5a. solution of model (26) is presented in Figure 5b.

Figure 5. Results of approximation of experimental data for Geren carcinoma.

MODELS OF COMBINED ACTION OF CYTOSTATIC AGENTS (INIHIBITORS) AND CARCINOGENS (PROMOTERS) Suggesting kinetic theory has important application for establishment of general regularities of tumor growth, revealing of its mechanisms and developing of objective criteria of estimation of activity of carcinogen and anti-tumoral substances. There are a lot of works in literature devoted to these questions. However until now there is no adequate kinetic model based on biology of cell growth.

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Calculation of critical values under transplantation of tumors and efficiency of action of anti-tumoral preparations may serve of one of illustrations of possibilities of considered model [6]. The following ratio may be used as criterion of inhibitor or promoter effect of action: Еt(х1,x2) = (Tx-То)/To

(35)

where Tx, Tо − periods of induction (incubation) at chemical reagents concentrations х1, х2 and in their absence. These values are calculated directly by equation (25). The values Еt(x) calculated by theoretical curves of tumor growth at definite values of coefficients are in agree with experimentally established effects [2].

5.1. Model of Promoters (Activators) Action It is of the essence that quasi-chemical models allow description of both inhibition and stimulation (promotion) of biological growth. Promotion action of additives on biological growth in considered kinetic theory is taken into account by introduction into equation (22) in an explicit form of dependence of coefficients of birth b and chain propagation p on promoter concentration. This dependence may be approximated by equation of Mono type for organisms or Michaelis-Menten for fermentative catalysis. Equation (22) for х1=х2=0, w1= 0 and f=2 is solved in relation to c1(t). Theoretical curves qualitatively correctly (Figure 6) reflects acceleration of growth of cells of mouse embryo Balb/c 3T3 [22] with increase of serum concentration containing stimulators. Action of carcinogens on tumor growth is described analogously.

Figure 6. Acceleration of growth of cells of mouse embryo Balb/c 3T3 [22] with increase of serum concentration containing stimulators.

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6. ECOTOXICOLOGIC MODEL OF PROLIFERATION Disturbance of proliferation of cells regulation is revealed as oncological desease. For control of proliferation disturbance they introduce into reduced ecotoxicological model together with normal growing cells and kariokynetic cells one more group − atypical cells. These cells form tumors. Mathematical model of growth of such heterogeneous population in accordance with kinetic graph (Figure 7) is reflected by the following system of equations:

dc1 = −p x c1 + f1bc m , dt dc m = p n c 1 − b x c m − a 1c 1c m − a 2 c a c m , dt dc a = f 2 p ax c1 − d x c a . dt

(36)

Figure 7. Kinetic graph of ecotoxicological model of tumor growth of equations system (37) solution.

Here p x = p a + p n + δ 1 x, b x = b + δ 2 x, p ax = p a − δ 3 x, d x = d + δ 4 x. , с1, cm, ca – numbers of growing, kariokynetic and atypical cells; a1, a2 – coefficients of autoinihibition at the expense of competition for general resource between growing, kariokynetic and atypical cells; pn, pa – coefficients of growth of normal and atypical cells; b – coefficient of population chain branching; d – rate of atypical cells extinction; f1, f2 – coefficient of kariokynetic and atypical cells reproduction; x – inhibitor concentration; δ1, δ2, δ3, δ4 – coefficient of toxic action of inhibitor on corresponding process. In normalized form the equations (36) are as follows:

dz 1 = − σ 1 z 1 + f 1µ 1 z 2 , dτ dz 2 = z1 − σ 2 µ1z 2 − µ1z 1z 2 − µ1z 2 z 3 , dτ dz 3 = f 2 σ 3µ 2 z 1 − σ 4 µ 3 z 3 . dτ

(37)

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where:

σ1 = 1 +

p a δ1 δ δ δ + x , σ 2 = 1 + 2 x , σ 3 = 1 − 3 x , σ 4 = 1 + 4 x, pn pn b pa d

(38)

p a b d µ1 = , µ 2 = a 2 , µ3 = . pn p n a1 pn In system (37) z1, z2 are numbers of growing and kariokynetic groups of cells normalized per capacity of medium without influence of toxicants in the absence of atypical cells; z3 – number of atypical cells notmilized per individual capacity of medium also without influence of toxicants; τ = pnt – extensible time.

z1 =

a1 a a c1 , z 2 = 1 c m , z 3 = 2 c a . b b b

Separation of characteristic time scales of two-stage growth allows simplifying of dynamics analysis. Ratio of characteristic times of growth of cells of the first z1 and the second z2 groups depends on parameter µ1 = b/p. If constants of rates of chain birth and propagation are correlated in such way that µ1 >> 1, then conditions of Tikhonov's theorem are fulfilled and full system (37) is reduced to degenerated equation:

χ − z1 − z 3 dz 1 = σ1 z 1 , dτ σ 2 + z1 + z 3

(39)

dz 3 = f 2 σ 3µ 2 z 1 − σ 4 µ 3 z 3 . dτ where:

χ=

f1 − σ 1 σ 2 . σ2

The example of solution of equations system (37) at initial conditions {z1(0) = 1, z2(0) = 0, z3(0) = 0} is presented in Figure 8. Stationary states of the whole system (37) are determined by expressions: (1)

( 2)

z1

(1)

(1)

z1 = 0, z 2 = 0, z 3 = 0; ( 2) ( 2) p + p + δ x ( 2) ( 2) σ µ (f − σ1σ 2 ) a (p − δ 3 x) (40) 1 a = 4 3 1 , z 2 = z1 n , z 3 = z1 f 2 2 a . σ1 (σ 4µ 3 + f 2 σ 3µ 2 ) f1b a1 (d + δ 4 x)

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It follows that for realization of effective anti-tumoral therapy one should select such chemical agent x which action on atypical cells in many times exceeds its influence on normal ones, i.e. δ3, δ4 >> δ1, δ2. by such effect one may significantly reduce stationary value ( 2)

z 3 and consequently kill population of atypical cells.

Figure 8. The curves of growth of normalized model (solution of equations system (37)) at pn = 1; pa = 1/5; b = a1 = a2 = d =1, δ1 = δ2= δ4 = 0,01; δ3 = 0,001; f1 = f2 = 2; x = 15. ( 2)

Let study stationary stages of equilibrium of atypical cells population z 3 at the change of coefficients of toxic action δ3, δ4 of toxicant x on rates of growth pa and loss d. ( 2)

The surface of stationary states z 3 (δ 3 , δ 4 ) at the change of weights δ3 and δ4 is shown ( 2)

in Figure 9a and in Figure 9b you may see sections of this surface at z 3 = const.

( 2)

Figure 9. The surface of equilibrium states z 3 (δ 3 , δ 4 ) . pn = 1; pa = 1/20; x = 1.

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One may reduce concentration of atypical cells by both at the expense of selection of medical substance and by increase of doze. By this action of substance is strengthened on both atypical and normal cells that leads to effect of side action of medical treatment. ( 2)

Change of equilibrium concentration z 3 as function of concentration of toxicant x and influence of this toxicant on growth rate δ3 are presented in Figure 10.

( 2)

Figure 10. The surface of equilibrium states z 3 (δ 3 , x) . pn = 1; pa = 1/5; δ4 = 1.

More advantageous approach in relation to organism is selective acceleration of rate of atypical cells loss under the action of medical substance. And this substance doesn't influence on rates of growth of all types of cells. Such situation of atypical cells loss is shown in Figure 11. The surface of stationary states ( 2)

z 3 (x, δ 4 ) is uniformly decreased with the rise of toxicant x concentration and strengthening of atypical cells sensitivity to medical effect δ4 at the expense of correct selection of the last one.

( 2)

Figure 11. The surface of equilibrium states z 3 (δ 4 , x ) . pn = 1; pa = 1/5; δ3 = 0,1.

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All mentioned above surfaces of equilibrium states contain special points of stable nodes type. Now let analyze reduced system (39). For it the special points are written in the following way: (1)

(1)

(1)

z1 = 0, z 2 = 0, z 3 = 0;

(2)

z1 =

( 2) (2) p + p + δ x ( 2) ( 2) σ 4µ 3 (f1 − σ1σ 2 ) a (p − δ 3 x ) 1 a , z 2 = z1 n , z 3 = z1 f 2 2 a . σ1 (σ 4µ 3 + f 2 σ 3µ 2 ) f1b a1 (d + δ 4 x )

(41)

With the change of toxicant x concentration in accordance with (41) the stationary ( 2)

occupancies z will be changed. Curves families of equilibrium numbers of atypical cells for set of coefficients values of toxic action δ3, δ4 = const are presented in Figure 12. The characteristic feature of these plots is the fact that at equal value of x extinction occurs faster at the value δ3 lower than δ4. This fact shows to the best advantage the action of toxicant namely on the rate of atypical cells growth, i.e. at successive selection of preparation at which δ3 is high one may faster and with higher efficiency inhibit population z3 than by other preparation but with the same amounts effecting on mortality via sensitivity coefficient δ4.

Figure 12. The family of phase-parametritic diagrams zst(x). a) δ3 = 0,01; δ4 = const; b) δ3 = const; δ4 = 0,01.

(2 )

Stationary state z 3

is changed with the change of coefficients of toxic action. Figure 3 (2 )

illustrates dependence z 3 (δ 3 ) at various values of x and δ4. Interesting particularity is noticeable in Figure 13a. Total extinction of population of atypical cells occurs beginning from the only value δ 3 =0,2. This fact means that it is possible to drive out population cr

completely only at ioncrease of parameter δ3 at the expense of selection of toxic preparation. However, Figure 14 shows that such tactics leads only to asymptotical reduction of level (2 )

z 3 down to zero at any levels of concentration of toxicant x and δ3. This fact testifies that while influencing only on population mortality it is impossible to destroy it completely.

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Figure 13. The family of phase-parametritic diagrams zst(δ3). a) δ4 = 0,01; x = const; b) δ4 = const; x = 1.

Figure 14. The family of phase-parametritic diagrams zst(δ4). a) δ3 = 0,01; x = const; b) δ3 = const; x = 1.

Figure 15. The dependence of roots of characteristic equation of system (37) on toxicant concentration.

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We should note that all equilibrium states listed above are stable nodes. It is obvious from Figure 15 in which substantial parts of roots of characteristic equation calculated on the (2 )

(2 )

multitude of equilibrium values z 1 and z 3 are presented as functions of toxicant concentration. Curves Re[p1] and Re[p2] lay in the region of negative values and consequently equilibrium values corresponding to them are stable nodes.

REFERENCES [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20] [21] [22] [23] [24] [25]

Yu.A. Ershov, Dokl. RAN, 352, No.5, 1 (1997) (in Russian). Yu.A. Ershov, Zh. Fhizicheskoi Khimii, 72, No.3, 553 (1998) (in Russian). Yu.A. Ershov, Oxidation Communications, 21, 441 (1998). Yu.A. Ershov, Applied Biochemistry and Microbiology, 35, No.3, 245 (1999). N.N. Semenov, On some problems of chemical kinetics and reaction ability, Moscow: AN SSSR (1958) (in Russian). N.M. Emanuel, Kinetics of experimental tumor processes, Moscow: Nauka (1977) (in Russian). H.E. Skipper, F.M. Schobel, W.S. Wilcox, Cancer Chemother. Rep., 35, 3 (1964). E. Schreck, Amer. J. Cancer, 24, 897 (1935). H.J. Bagg, J. Jackson, Amer. J. Cancer, 30, 539 (1937). W.C. Summers, Growth, 30, 333 (1966). W.R. Laster, et al., Cancer Chemother. Rep., Part I, 53, 169 (1969). V.V. Alekseev, I.I. Kryshev, Physical and Mathematical Modeling of Ecological Systems, St. Petersburg: Gidrometeoizdat (1992) (in Russian). A.D. Bazykin, Mathematical Biophysics of Concurrent Populations, Moscow: Nauka (1985) (in Russian). Yu.A. Ershov, T.V. Pleteneva, T.K. Slonskaya, Bull. Experiment. Biologii i meditziny, No.5, 594 (1997) (in Russian). Yu.A. Ershov, N.B. Esmenskaya, T.K. Slonskaya, Khim.-farmatz. Zh., No.11, 6 (1995) (in Russian). Yu. Odum, Basic Ecology, Philadelphia: Saunders (1983). M. Begon et al., Ecology: Individuals, Populations, and Communities, Oxford: Blackwell (1986). Yu.A. Ershov, N.N. Moshkamborov, Kinetics and thermodynamics of biochemical and physiological processes, Moscow: Meditzina (1990) (in Russian). G.S. Yablonskii et. al., Kimetic models of catalytic reactions, Novosibirsk: Nauka (1983) (in Russian). Mathematical problems of chemical kinetics, Ed. by K.I. Zamaraev, G.S. Yablonskii, Novosibirsk: Nauka (1989) (in Russian). S.D. Varfolomeev, S.V. Kalyuzhnyi, Biotechnology. Kinetic bases of micro-biological processes, Moscow: Vyssh. Shkola (1990) (in Russian). O.S. Frankfurt, Cellularr cycle in tumors, Moscow: Meditzina (1975) (in Russian). D. Khimmel'blau, Ananlysis of processes by statistical methods, Moscow: Mir (1973) (in Russian). Biological cells in culture, Leningrad: Nauka (1984) (in Russian). http://www.pivnik.ru/works/new/newmet_020_1.doc.

In: Chemical and Biochemical Physics: New Frontiers ISBN 1-60021-165-8 Editor: G. E. Zaikov, pp. 113-125 © 2006 Nova Science Publishers, Inc.

Chapter 12

ONE-STAGE METHOD OF CATALYTIC OXIDATION OF VEGETAL RAW MATERIALS BY OXYGEN: NOVEL ECOLOGICALLY PURE PRODUCTS AND PERSPECTIVES OF THEIR PRACTICAL USE A. M. Sakharov N.M. Emanuel's Institute of Biochemical Physics Russian Academy of Sciences, Moscow, Russia

INTRODUCTION Ecological problems become one the main problems of humanity during last years. Chemical industry takes one of the first places among origins of dangerous pollutions of the environment and in this connection the search of principally novel chemical processes differing by lower level of energy consumption and minimum formation of side products is necessary. This fact relates to practically all chemical processes including processes of organic compounds oxidation by oxygen which allow obtaining of the wide spectrum of necessary products for various branches of industry and agriculture. Professor N.M. Emanuel was at the beginning of works on search of principally novel processes of organic compounds oxidation by oxygen differing by high productivity and formation of minimum amounts of side products. As it is consequent from fundamental works of N.M. Emanuel the most perspective direction for increase of selectivity of reactions of liquid-phase oxidation is the use of metal complex catalysis [1]. In this case application of corresponding ligands allows changing of catalysts structure and properties in such way to make proceeding of side process unfavourable. In works made under direction of N.M. Emanuel they showed that catalytic system [Cu2+…A-…O2] where А- − the anion form of substrate (anion form of substrate was formed at the expense of its deprotonation under the action of bases introduced into the system) is extremely effective in reactions of oxidation of fluorinated alcohols with general formula H(CF2CF2)nCH2OH (where n=1-6) [2], camphor [3] and diacetone-L-sorbose [4] with

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formation of correspondingly fluorine-containing acids H(CF2CF2)nCОOH, camphor and diacetone-2-keto-L-gulone acid. As the investigation of alcohols oxidation reactions mechanisms in the presence of copper and bases ions showed the participation of Cu2+ in the process of electrons transfer from coordinated anion form of substrate to O2 molecule opened possibility of reaction proceeding by concert multi-electron mechanism without formation of free radicals. Proceeding of process by thermodynamically advantage multi-electron mechanism of oxygen reduction allows reaching of high rates of oxidation at room temperatures at selectivity of formation of final products exceeding 90% [5]. Process of oxidation of organic compounds by oxygen in the presence of copper compounds and bases may be widely applied in the field of processing of nature raw materials. One of the most interest directions in the field of large-capacity chemistry at present is its sharp turning in favor of using of products of native origin as initial raw materials for synthesis of reagents used in various branches of industry. The novel chemistry calling "green" chemistry is conceived. The process of oxidative modifying of starch and other polysaccharides with obtaining of valuable oxygen-containing products differing by improved properties in comparison with initial compounds takes important place in it. The methods of oxidative modifying of polysaccharides with receiving of polyacids as main products are widely used in practice due to availability of initial raw material and high consumer properties of oxidized polysaccharides. Salts of polyacids are widely used as watersoluble glues in production of paper, cardboard, in processes of materials dressing, as components of drilling agents, etc.. However, as well as for a lot of other processes of organic compounds oxidation as oxidizing agent of polysaccharides the hypochlorites and periodates [6, 7], hydrogen peroxide [8] and not gaseous oxygen are used till recently that is connected with low activity of oxygen in processes of polysaccharides oxidation. It turned out that in the presence of copper complexes and bases not only simple in their structure alcohols and ketones but also polysaccharides (starches, dextranes, cellulose) may be oxidaized by oxygen with high rates. High rates of polysaccharides oxidation by oxygen exceeding oxidation rates by hypochlorites and other oxidizing agents are reached at temperatures 40-90°C [9-11]. As well as under oxidation of monoatomic alcohols [5] the anion form of substrate (A- − deprotonated polysaccharide) forms the adducts (Cu2+…A-) with copper ions and the role of catalyst, Cu2+ ions is to activate deprotonated form of substrate in relation to oxygen. We may suppose that role of divalent copper is in oxidation of substrate anion form with following interaction of intermediate radicals or anion radicals with O2. However high-molecular polysaccharides with low content of end aldehydes groups in anaerobic medium are redoxinactive and the rate of valent transitions Cu2+→Cu+ at the expense of electron transfer from substrate anion form to Cu2+ proceeds with rates in dozens of times lower in comparison with the rate of oxygen adsorption during the process of polysaccharides oxidation in alkaline mediums. They showed that namely direct interaction of oxygen with anions A- in coordination sphere of copper ion led to formation of hydroxycarboxylates as main primary products of oxidation [12]. Absorption of oxygen is completely stopped after neutralization of introduced alkali by formed during the oxidation process polyoxyacids. Thus, by varying of amount of introduced alkali we may change the degree of polysaccharides oxidation into

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polyacids. This allows changing of final products viscosity, bonding ability, solubility in water, etc.. As initial raw materials for receiving of salts of polyoxyacids one may use not only starch, but any other starch-containing raw materials: corns of maize, oats, rice, etc., including ill-conditioned raw materials (grain-crops affected by various fungus diseases, waste of rice slashing, waste of mill houses, etc.) [9, 10]. This fact allows decreasing of prime price of final product production in dozens times. Oxidized starch-containing reagents (OSR) may be used as ecologically pure reagents in production of resin-bonded chipboard and cane fiber board, components of drilling solutions and oil-removing liquids, as components of architectural mixtures, fire-retardant additives relating to the class of coke-forming extinguishants, components of cleansers, stimulators of plants growth and in a number of other fields where modified and non-modified polysaccharides are used.

APPLICATION OF OXIDIZED STARCH-CONTAINING REAGENTS (OSR) AS BINDING AGENTS IN PRODUCTION OF RESIN-BONDED CHIPBOARD AND CANE FIBER BOARD Oxidized starch-containing raw materials obtained from both starch and starch-containing raw materials (for example from affected amaize corns) may be used as ecologically pure bonding agents in production of resin-bonded chipboard and cane fiber board [9, 10]. Table 1. Physical-mechanical characteristics of resin-bonded chipboard obtained with the use of mixture of phenol-formaldehyde resin (KF-MT) with OSR* Structure of bonding agent, mass % KF-MT – 100 OSR – 0 KF-MT – 95 OSR – 5 KF-MT – 90 OSR – 10 KF-MT – 85 OSR – 15 KF-MT –80 OSR – 20 KF-MT – 75% OSR – 25% *

Density, kg/m3

Breaking point at bending, MPa

Tensile strength, MPa

708

11,9

0,11

711

12,2

0,12

726

13,4

0,15

704

12,5

0,15

725

12,1

0,16

717

15,0

0,17

OSR was obtained by oxidation of affected maize corns and represented water solution of polyacids salts with the content of dry substances 17 mass %

Particle board with sizes 600 ¯ 600 ¯ 16 mm was obtained in laboratory conditions with the use of mixtures of OSR and phenol-formaldehyde resin of KF-MT brand. OSR was introduced as 17 mass % water suspension. Physical-mechanical characteristics of these

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boards are presented in Table 1. As it is obvious from this Table substitution of the part of phenol-formaldehyde resin by OSR leads to strengthening of boards. However, the most important feature of OSR usage is lowering of toxicity of boards at the expense of decrease of diffusion of phenol and formaldehyde from particle board samples. As tests showed, toxicity of boards under the use of OSR as one of the bonding agent in mixture with KF-MT was reduced by 30÷40% in comparison with boards obtained with the use of one KF-MT.

2. OSR AS COMPONENTS OF DRILLING SOLUTIONS AND OIL-SWEEPING LIQUIDS At present water-soluble polymers are widely used in oil-production branch of industry as lowers of water filtration of drilling solutions, oiling additives, plasticizers, corrosion inhibitors, etc.. As carried out laboratory and industrial tests showed oxidized starch reagents might be successfully used as main components of drilling solutions on water base and might substitute expensive carboxymethylcellulose (CMC) and reagents on acrylonitrile base applied at present. And in many cases technological properties of drilling solutions are improved [13]. It is extremely important that oxidized starch reagents are highly effective corrosion inhibitors of black metals [14] that reduces costs on carrying out of drilling operations connected with equipment deterioration. One the most important properties of drilling solutions assigned for drilling in unstable depositions is their dispersion ability which determines possibility of maintaining of the minimum permissible concentration of solid phase in solution. Ability of salts of oxidized polysaccharides to adsorb on stratum particles surface screening active zones and preventing transition of these particles into structure forming phase of drilling solution opens wide perspectives of OSR application as highly effective inhibitors of drilling solutions. Inhibiting ability of OSR is sharply increased when substituting the part (about 50%) of Na or K ions by multivalent cations: Ca, Fe, Al and this is reached by simple addition of water-soluble salts of listed metals to water OSR solutions. The data on inhibiting ability of drilling solutions treated by OSR (K-Ca and K-Al-forms in comparison with non-treated solutions and treated Na-CMC (sodium salt of carboxymethylcellulose are widely used at present reagent for drilling solutions)) are presented in Table 2. Inhibiting ability was determined by the following technique: bentonitic clay in the form of grit with particles sizes 3mm in amount of 25g was introduced into 500ml of tested solution and mixed for 4 hours. Then the solution was passed through the system of vibration sieves with cells sizes 3, 2 and 1mm. Separated on sieves fractions were dried until constant weight at temperature 105°C and their weight percent was determined in relation to introduced amount of clay. Analyzing the data presented in Table 2 we may conclude that application of OSR as drilling solution inhibitor (Ca-K and Al-K-form) leads to significantly higher dispersion of grit in comparison with solutions treated by Na-CMC. Solutions containing aluminapotassium modification of OSR (oxidized affected maize corns in which 50% of potassium ions are substituted by ions of three-valent aluminum) possesses the lowest dispersion ability that opens wide possibilities of usage of this modification as component of drilling solutions.

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Table 2. Inhibiting ability of drilling solutions treated by OSR.

Structure of drilling solution Initial bentonitic solution + 1,5% Na- CMC + 1,5% -OSR К-Са-form + 1,5% -OSR К-Аl-form

Fractional structure of grit, mass % not less than from 2 to from 1 to 2 3 mm 3 mm mm 22,7 30,3 12,4 18,0 20,0 16,1 77,8 11,8 1,4 11,8 0,8 83,4

Total amount of grit, mass % 65,4 56,3 92,0 95,3

OSR may be used in structure of oil-sweeping liquids. Injection of polymers water solutions into heterogeneity layers provides oil recovery at the expense of increase of coefficients of layer coverage as a result of decrease of ratio of water mobility and displaced oil. At present for oil displacement from layers carboxymethylcellulose (CMC) are the most widely used. However, wide application of CMC in oil-production industry is limited by limited volumes of its production and high cost [15]. OSR as it was already mentioned was significantly cheaper than CMC and might be obtained from agricultural waste that makes it even more advisable. Laboratory experiments on testing of possibility of OSR application as additive to water with the aim of its densifying and improvement of washing properties were carried out on the plant modelling the process of oil displacement from porous stratum at given rate of filtration and pressure close to real observed [16]. Final coefficients of oil-recovery were calculated as ratio of oil mass displaced from model to oil mass initially containing in porous stratum. In Table 3 we present the data on influence of viscosity of CMC and OSR water solutions on oil-recovery coefficient for two types of oils. Received data testify that water solutions of OSR possess higher oil-sweeping properties in comparison with CMC solutions of the same viscosity. This fact is explained by higher surface activity of OSR solutions on the interface with oil [16]. Table 3. The influence of viscosity of OSR and CMC water solutions on oil-recovery coefficient Oil-recovery coefficient, % Reagent

*

Viscosity, mPa⋅sec

Romashkinskaya oil*

Pionerskaya oil*

Water

1,0

46,8

34,4

CMC OSR CMC OSR CMC OSR CMC OSR

1,4 1,4 5,0 5,0 10,0 10,0 20,0 20,0

52,3 54,2 57,3 60,9 60,1 65,0 61,9 68,5

39,5 41,5 43,4 45,2 46,1 48,2 48,2 50,8

Romashkinskoe oil-filed: viscosity is 15Pa⋅sec, Pionerskoe is 226 Pa⋅sec.

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OSR may be used as high-effective isolating agent in flow-deflecting technologies allowing intensification of production of residual oil. It is connected to a great extent with unusual effect of interaction of OSR solutions with boric acid. It turned out that additives of small amounts of boric acid to OSR gels (of low degree of oxidation) lead to formation of high-viscous structured gels possessing non0linear-viscous properties [17, 18]. And such effect is reached already at weight ratio OSR/H3BO3=100 in calculation to dry substance. Structuring of gels occurs (at content of OSR in water more than 5-10 mass %) practically immediately after addition of small amounts of boric acid solution to water solution of OSR. Such gels possess over-anomalous rheologic properties. Dependence of viscosity on deformation rate for 15% solution of OSR (oxidized rice) as without additive (curve 1), so with addition of Н3ВО3 (curve 2) are presented in Figure 1. Content of boric acid is 1,5 mass %. It is obvious that addition of boric acid to gel of OSR sharply changes rheologic properties of system. Dependence of shear stress on deformation rate takes extreme character with minimum in the region 5 sec-1 that testifies t formation of gel structure strong enough. The region of sharp linear growth up to the rate of deformation 5,5 sec-1 corresponds to undestructed structure and system behave at Shvedov-Bengam solid with plastic shear stress equal to 0,17Pa and structure viscosity 1,45 Pa⋅sec. Decrease of shear stress at further increase of deformation rate indicates on spatial structure, and the following linear section of curve is connected with complete destruction of gel structure and system acts as Newton liquid with viscosity 0,13 Pa⋅sec. 14

2

shear stress, Pа

12 10 8 1

6 4 2 0 0

20

40

60

80

shear rate, 1/sec

Figure 1. Dependence of viscosity on deformation rate for 15 mass % solutions of OSR (oxidized rice). 1 − boric acid concentration is 1,5 mass %, 2 − without addition of Н3ВО3.

The viscosity of cross-linked by boric acid OSR gel with undestructed and destructed structures is differed in more than 10 times that allows suggesting of given reagent as isolating agent in flow deflecting technologies. At high rates of flow in tubes and bottomhole formation zone the solution of cross-linked OSR will possess low viscosity and will be easily injected. At low rates of deformation in layer depth the given system will behave as viscous plastic and isolate high-permeability stratums.

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3. APPLICATION OF OSR IN ARCHITECTURAL MIXTURES Oxidized starch and oxidized starch-containing raw materials may find wide application in construction industry. As investigations showed, additives of OSR allowed imparting large plasticity to cement solutions and increasing strength of both cement and concrete solutions after drying. OSR may be used as gluing additive for filling, emulsion paints and also for producing of heat- and soundproof materials. OSR are effective decelerators of plaster and concrete hardening. The dependence of plaster hardening time on concentration of introduced OSR is presented in Figure 2 (oxidized maize corns, curve 1). The data on the influence on CMC hardening time (curve 2) and lignosulfonate (curve 3) widely used at present as bonding agents are presented for comparison. As it is obvious from the Figure the OSR possess significantly higher exploitation properties as decelerator of plaster hardening in comparison with known bonding agents. 80 Time of hardening (stiffening), min.

1

60 2 40

3 20

0 0

0,25

0,5

0,75

1

Additive concentration, mass % Figure 2. Dependence of hardening (stiffening) time of plaster on concentration of additives, mass %: 1 − CMC, 2 − lignosulfonate, 3 − OSR (oxidized maize corns).

Estimation of quality of dry plaster mixtures under the use of OSR as bonding agent showed that fillings were differed by high elasticity, were easily leveled on surface of wall and possessed high adhesion to various surfaces. The data on influence of OSR (oxidized rice and oxidized maize corns) on physicalchemical properties of dry architectural mixtures on the base of plaster and vermiculite (ratio plaster: vermiculite = 7 : 3) are presented in Table 4. As it is obvious additives of OSR allow significant increasing of both time of stiffening and samples (arms) strength.

120

A. M. Sakharov Table 4. Physical-chemical properties of dry plaster-vermiculite mixtures with the use of OSR OSR amount (mass % by plaster) ----12∗ 33∗ 31∗∗

*

Time of stiffening, min beginning

end

9 19 18 25

12 30 90 150

Compressive resistance, kg/m2 3,12 5,70 4,80 8,40

Heat conduction coefficient, Vt/m.degree 0,13÷14 0,13÷14 0,13÷14 0,13÷14

oxidized rice; oxidized maize

**

OSR may be used in production of ecologically pure fillings. Carried out investigations of fillings on chalk base with additives of OSR showed that they possessed wonderful physical-mechanical properties. So, strength of cohesion of fillings containing OSR as bonding agents with concrete is more than 5 kg/cm3 and of all-Union State Standard 24064 require not less than 1,5 kg/cm2.

OSR AS WATER-SOLUBLE ADDITIVE FOR INCREASE OF FIRE EXTINGUISH ABILITY OF WATER AND ANTIPYREN As investigations showed, oxidized starch reagents may be applied as effective fireprotective impregnations, antipyren additives under production of various polymer materials on the base of water-soluble polymers and latexes, and also under fire extinguishing [19]. Obtained results turned to be very surprising since nobody assumed that starch-containing reagents might possess high fire extinguishing properties. Determination of oxygen index (OI, minimum oxygen content in air at which samples burning begins) for various paper types, sawdusts and synthetic materials show that OI in all cases exceeds 25%, and in some cases exceeds 40% [19]. Thus, OSR may be recommended as component of impregnation fire-protecting compositions. Water solutions of OSR possess significantly higher fire extinguish ability in comparison with pure water. Influence of OSR additives (oxidized potato starch) on fire extinguish efficiency of fine-disperse water was estimated by decrease of average time of burning process quenching of cotton fabric impregnated by otor oil AS-8. At other equal conditions introduction of OSR into water in amount 50÷150 g/l allows decreasing of extinguishing time from 15÷16 sec down to 10÷6 sec [19]. As investigations show OSR may find application as file-protecting coverings for wood products. At present wood is one of the most widely used architectural materials due to its relatively high strength, low thermal conductivity and density, easiness of mechanical treatment, etc.. the main disadvantage of wood under the use in construction is its high fire risk. One of the most prevalent method of decrease of wood combustibility is application of antipyrens. In ideal case antipyrens should reduce all parameters of fire risk: combustibility, inflammability, flame spreading on surface, smoke-forming ability and toxicity of burning

One-Stage Method of Catalytic Oxidation of Vegetal Raw Materials by Oxygen

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products. As investigations show, these strict requirements are fulfilled when one uses oxidized starch reagents as antipyrens [20-22]. Among great number of developed means of fire-protection the most effective are coverings and compositions of foaming type. The compositions on the base of OSR are in particular such substances. The mechanism of fire protecting action of such coverings is bonded with formation on treated surface at high-temperature heating or at direct influence of fire of foamed coke layer. The layer of foam-coke reveals heat-protecting and barrier effects at mass-transfer of both combustible materials to zone of flaming reaction and of air oxygen to material surface. Results of estimation of efficiency of fire protecting action of coverings on the base of oxidized starch-containing raw materials on amount of applied reagent carried out by standard method (all-Union State Standard 16363-98) are presented in Figure 3. As it is obvious, all compositions already at one-layer covering of pine samples by oxidized starch reagent (with consumption of OSR 100 g/m2) provide fire-protection of the II group and reaching of rank of hardly-inflammable wood. With increase of covering number up to 3÷4 (OSR consumption 300÷400 g/m2) mass losses at fire testing are significantly decreased and studied antipyrens allow obtaining of the I group of fire-protection − hardly-inflammable wood. Important index of fire risk is toxicity and smoke-forming ability of materials. According to statistics 70% of cases of people death in conflagrations occur due to poisoning by toxic products of burning, in particular carbon oxide. Strong bloom during conflagration plays decision role in appearing difficulties under people evacuation from buildings and under conflagration localization and liquidation.

30

25

mass loss, %

20

15

10 3 2

5

1

0 0

100

200

300

400

500

2

Consumption, g/m

Figure 3. Dependence of mass losses of wood samples on amount of applied fire-protecting coverings on the base of modified polysaccharides: 1 − oxidized starch (high degree of oxidation), 2 − oxidized rice (high degree of oxidation), 3 − oxidized starch (average degree of oxidation).

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Index of toxicity of untreated pine (HCL50) in smouldering regime (450оС) is equal to 31,4 g/m2 (high toxicity). At the same temperature the sample treated by OSR have average toxicity (HCL50 = 46÷50 g/m3). In regime of fire combustion of wood (750оС) the products of burning of untreated wood are formed in amount presenting high danger (HCL50=33,2 g/m3). Treatment of pine surface by OSR compositions in this case also allows decreasing of poisoning danger in several times [21]. Results of investigations of heat generation characteristics under wood combustion with coverings on the base of OSR also confirm high efficiency of their fire-protecting action. The mechanism of fire protection together with foaming and carbonization of covering (OSR) with formation on the surface of wood of coke layer with high heat-isolating ability is obviously also connected with the change of thermal-chemical properties of materials [22].

5. APPLICATION OF OSR AS COMPONENTS OF DETERGENTS Oxidized starch reagents may be used in washing powders as substituents of polyphosphates [11]. As investigations show OSR possess the number of unique physicalchemical properties allowing hoping on their application as one of the main components of detergents. One of the most important characteristics of detergents is their ability to remove adhered to surface contamination particles and transfer them into suspension state. If there is liquid oil dirt the improvement of selective moistening promoting pushing off of dirt by water solutions of detergents from washing surfaces plays important role. The characteristic of selective moistening is the value of contact angle of oil drop on glass surface. Technique of experiments of determination of reagents efficiency in the structure of detergents was in the following: oil drop was placed on glass surface, then the glass was placed into investigated solution containing OSR and with the help of horizontal microscope the contact angle was measured (oil drop was in water solution at the lower surface of glass). Maximum time of contact angle measuring was 20 min. As tests showed oxidized starch reagents of various nature significantly reduced contact angle of moistening, and their mixtures with isopropyl alcohol (2 mass % of OSR + 0,6 mass % of isopropanol) caused drop dispersion (Table 5). Table 5. The values of contact angles of selective moistening of oil drop on glass by solutions containing OSR Solution Water Wtaer + 2 mass % of OSR (oxidized rice) The same + 0,6 mass % of isopropanol

Value of contact angle, α 130о 70о Oil drop is dispersed

The most interesting results were obtained under investigation of dispersion ability of OSR mixtures with sodium dodecylsulfate. Results of influence of OSR mixture structure (oxidized rice) with sodium dodecylsulfate on value of contact angle of moistening are presented in Table 6. As it is obvious from Table 6 moistening ability of OSR is lower than for solutions of sodium dodecylsulfate. But the most surprising fact is that solutions with low

One-Stage Method of Catalytic Oxidation of Vegetal Raw Materials by Oxygen

123

content of sodium dodecylsulfate and high content of OSR content possess highest moistening ability. Such compositions are differed by unique high moistening ability and causes practically immediate dispersion of oil drop and its washing way from glass surface. Table 6. Influence of composition structure sodium dodecylsulfate / OSR (oxidized rice) on the value of contact angle of moistening Components content in solution, g/l Sodium OSR dodecylsulfate 4,8

0

3,0

1,8

2,4

2,4

0,9

3,9

0,24

4,56

0

4,8

Change of contact angle, α

Results of observation

After 2-3 min. oil drop goes away from glass surface After 2-3 min. oil drop goes away from glass о о 90 -30 surface After 1 min. drop splitting starts and then drop о о 120 -40 goes away from glass surface After 1 min. drop splitting starts and then drop 110о-40о goes away from glass surface Practically immediately the angle is increased down to 30° and drop goes away from glass surface For 15 min the angle is not changed. Detachment 120о-45о of drop is observed in two cases from10. 60о-30о

Thus, substitution of the main part of expensive anion SAS by cheap reagents (OSR) may lead to both reduction of prices of detergents and to increase of their efficiency.

6. APPLICATION OF OSR AS FILM FORMING SUBSTANCE FOR PREPLANT TREATMENT OF SEED Preplant treatment of seed by pesticides with addition of film-forming substances (incrustation of seed) gives possibility of dosage of protectant amount with high accuracy and it is effective mean of fixation of pesticides, growing stimulating substances, microelemts, etc around the seed. Sodium salt of CMC (Na-CMC) is widely used in incrustation processes. Disadvantages of Na-CMC as film-forming substance are high viscosity of recommended for treatment solutions, often seed conglutination, and also comparatively low adhesion and consequently significant sloughing of pesticides and other components from seed surface. The growth of scale of seed incrustation application poses the problem of application of cheap, non-toxic and fast decomposing in soil reagents as film formers. As investigations showed OSR related to such type of substances. Composition, containing OSR are well soluble in cool water, possess optimal viscosity, after drying on seed stable film is formed. The data on films strength on seed durfaces with the use of Na-CMC and OSR as incrustrator (oxidized maize corns) are presented in Table 7. As it is obvious from this Table OSR form on seed surfaces significantly more strength to sloughing films in comparison with Na-CMC.

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Table 7. Sloughing of films containing tetramethylthiuramdisulfide (TMTD) as protectants from the surface of maize corns with the use of Na-CMC and OSR as film forming substances after 30 min of agitation Sloughing of film after 30 min of agitation, % to initial amount Film formatting agent

Na-CMC CMC (from maize corns)

Content of TMTD (g/kg of seed) 0,5

1,0

36,0 8,0

56,0 10,0

As investigations showed OSR form stable to sloughing films and possessed pronounced stimulating properties [23] that significantly broadened the field of application of reagents of such type in agriculture. Presented examples show that under the use of oxygen as the most cheap and ecologically pure oxidizer and simple catalytic system [Сu2+…substrate…base] we are succeeded in developing of principally novel processes of oxidative modification of vegetable raw materials with obtaining of valuable from practical point of view products. Invaluable contribution into developing of such processes was made by Professor N.M. Emanuel who stood at the beginning of works.

REFERENCES [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16]

N.M. Emanuel, Uspekhi khimii, 47, No.6, 1329 (1978) (in Russian). Certificate of authorship 1026416 USSR. Certificate of authorship 1129875 USSR. Certificate of authorship 1462751 USSR. I.P. Skibida, A.M. Sakharov, N.M. Emanuel, Itogi nauki i tekhniki, Ser. Kinetika i kataliz, 15, 110 (1985) (in Russian). M. Floor, A.P.G. Kieboom., H. van Bekhum, Starch, 41, 303 (1989). E. Santacesria, F. Trulli, G.F. Brussani, D. Gelosa, M.Di Serio, Carbohydrate Polymers, 23, 35 (1994). Stefan J.H.F. Arts, Erwin J.M. Mombarg, Herman van Bekkum, Roger A.Sheldon, J. Synhtesis, No.6, 597 (1997). I.P. Skibida, An.M. Sakharov, A.M. Sakharov, International application published in accordance with patent cooperation (РСТ), WO 93/15094 (1993). Patent 2017750 Russia. Europe Patent 0548399 (1993). A.M. Sakharov, I.P. Skibida, Khimicheskaya fizika, 20, No.6, 101 (2001) (in Russian). Certificate of authorship 1828118 USSR. Certificate of authorship 1542100 USSR. L.E. Lenchenkova, Nedra, 393 (1998) (in Russian). A.Yu. Serebryakov, A.A. Balepin, A.M. Sakharov, Nauka i tekhnologiya uglevodorodov, No.2, 73 (2003) (in Russian).

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[17] T.I. Zainetdinov, Dissert. Of candidate of technical sciences, Ufa (1999) (in Russian). [18] A.G. Telin, T.I. Zainetdinov, I.P. Skibida, A.M. Sakharov, Proceeding of an International Conference on Colloid Chemistry and Physical-Chemical Mechanisms, Moscow (1998) (in Russian). [19] Patent 2204547 Russia. [20] A.B. Sivenkov, B.B. Serkov, R.M. Aseeva, A.M. Sakharov, P.A. Sakharov, I.P. Skibida, Pozharovzryvoopasnost', 11, No.1, 39 (2002) (in Russian). [21] A.B. Sivenkov, B.B. Serkov, R.M. Aseeva, A.M. Sakharov, P.A. Sakharov, I.P. Skibida, Pozharovzryvoopasnost', 11, No.2, 21 (2002) (in Russian). [22] A.B. Sivenkov, B.B. Serkov, R.M. Aseeva, A.M. Sakharov, P.A. Sakharov, I.P. Skibida, Pozharovzryvoopasnost', 11, No.3, 13 (2002) (in Russian). [23] Certificate of authorship 1692006 USSR.

In: Chemical and Biochemical Physics: New Frontiers ISBN 1-60021-165-8 Editor: G. E. Zaikov, pp. 127-148 © 2006 Nova Science Publishers, Inc.

Chapter 13

EPR-SPECTROSCOPY OF COMPLEX POLYMER SYSTEMS A. M. Wasserman and M. V. Motyakin N.N. Semenov's Institute of Chemical Physics Russian Academy of Sciences, Moscow, Russia

INTRODUCTION Professor Nikolai M. Emanuel paid great attention to creation of development of novel methods of chemical physics. One of such methods is EPR-spectroscopy. In Department directed by Nikolai Emanuel the method of EPR-spectroscopy of spin marks and probes, in particular with the aim of investigation of polymer and polymer systems was actively developed. Special attention Nikolai M. Emanuel paid to the problem of chemical physics of polymer ageing and stabilization. Results obtained at that time were summarized in monograph by N.M. Emanuel and A.L. Buchachenko [1]. We shall consider only some results of investigation of complex polymer systems by method of EPR-spectroscopy obtained recently (results obtained earlier were considered in details in works [2, 3]). We shall discuss possibilities of method of EPR-spectroscopy of spin marks and probes for determination of macromolecules conformation in solid state, and also the results of investigation of molecular dynamics and organization of micelle systems − complexes polyelectrolyte−SAS. We shall also discuss some results obtained with the use of method of EPR-spectroscopy and its modification − the method of EPR-tomography for revealing of particularities of spatial distribution of active sites resulted from process of thermo-oxidative destruction of solid polymers.

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1. EPR-SPECTROSCOPY OF SPIN-MARKED MACROMOLECULES AS THE METHOD OF POLYMER CHAINS DETERMINATION IN AMORPHOUS SOLID POLYMERS Determination of macromolecules conformations is one of the basic problems of science about polymers. Simultaneously with development of theory [4-6] the perfection and enrichment of experimental methods of determination of macromolecules conformations in various phase and aggregate states occurs. However the method of neutron scattering was almost the only one method allowing reliable determination of polymer chains conformation in solid amorphous state until now [7]. Not long ago they begun to use with this aim also the method based on measurement of rate of electron excitement transfer between molecules of chromophores covalent bonded with polymer chain [8]. In works [9, 10] the method of polymers chains conformations determination in solid state based on the use of EPR-spectroscopy of spin-marked macromolecules was proposed. When solving this problem the analysis of dipole broadening of EPR bands by spin markers covalent bonded with polymer chain is carried out. Usually in physical chemistry of polymers they consider three states of flexible polymer chain: Gauss ball, swollen ball and globule. The state of swollen ball is characteristic for macromolecule in "good" solvent in which interaction polymer−solvent prevails over interaction polymer−polymer. Macromolecule has configuration of Gauss ball in θ−solvent in which interaction between units of polymer chain doesn't differ from interaction polymer−solvent. State of globule is realized in "bad" solvent in which intramolecular interaction of polymer units significantly exceeds interaction of macromolecule's units with solvent [4-6]. The ratio between average square of distance between two ends of polymer chain and polymerization degree P for macromolecule is usually written as follows [6]: = P2να2

(1)

here α − mean-square length of monomer unit, i.e. effective length which falls at one monomer (the value α characterizes the polymer chain rigidity); ν − coefficient characterizing conformational state of polymer chain. Coefficient ν depends on macromolecule conformation: for Gauss chain it is ν = 1/2, for swollen in "good" solvent ball it is ν = 3/5 (more accurate value is ν =0,592/11/), for globule it is ν =1/3/4-6/. The problem of determination of average square of distance between end of linear chain is come to determination of parameters ν and α in equation (1). The procedure of determination of parameter ν is come to determination of parameter ∆ for frozen (at 277K) solution of spin-marked polymer. This parameter depends on dipoledipole broadening of EPR-spectra of spin markers and probes [12]: ∆ = d1/d – (d1/d)0

(2)

where d1/d – the ratio of sum intensity of end components of spectra to intensity of central component at given concentration of paramagnetic sites; (d1/d)0 − the value of parameter d1/d

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129

at such concentration at which dipole broadening is not revealed in EPR-spectra (Figure 1). Then the solution of spin probe is selected (solution of nitroxyl radical not bonded with macromolecule) in the same solvent in which parameter d1/d has at 77K the same value, as for solution of spin-marked polymer; spectra of markers and probes are normalized by equal concentration of paramagnetic sites and the ratio of intensities of central components of spectra of probe (dp) and marker (d1) is determined. This ratio is compared with theoretical dependences of ratio dp/dl on parameter ∆ calculated for three conformational states of macromolecule: Gauss ball, swollen ball and globule (Figure 2). Such comparison allows selecting form three conformational states of polymer chain.

Figure 1. Examples of EPR-spectra of solutions of spin-marked poly-4-vinylpyridine (PVP-1, polymerization degree P = 500) (0,5 mass %) in methanol at 77K. The number of markers on polymer chain: 85 (1) and 3 (2).

For determination of the value of α in equation (1) it is necessary to compare the experimental value of parameter ∆ with theoretical; theoretical dependences of parameter ∆ on content of spin markers on macromolecule (β=m/P, here m − the number of units of macromolecule containing spin marker) at various values of α for Gauss and swollen chains are presented in works [9, 10]. If we know values of α and ν from ratio (1) we may easily calculate the mean-square distance between ends of polymer chain. The method described here was used for determination of conformational state and distance between polymer chain ends of various spin-marked polymers.: poly-4-vinylpyridine (PVP*), polymethacrylic acid (PMAA*), sodium salt of polymethacrylic acid (PMAA*-Na), styrene and maleic anhydride copolymer (STMAL*) [9, 10, 13] (formulas of spin-marked macromolecules are presented in Scheme 1; molecular masses of polymers and used solvents are presented in Table 1).

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Figure 2. Theoretical dependences of ratio of central components of normalized (corrected to one concentration of paramagnetic sites) EPR-spectra of probe (dp) and marker (d1) on parameter ∆: I − globule, II − Gauss chain, III − swollen in "good" solvent ball. Points are experimental values of ratio dp/dl, 77K. Number of points correspond to numbers of systems in Table 23.1.

In Figure 2 the experimental values of ratio of intensities of normalized EPR-spectra of probe and markers in solid state (at 77K) for systems presented in Table 1 are compared with theoretical; it is obvious from these data that conformational state of all investigated systems correspond to conformation of Gauss ball. In other words, in solid polymers and also in used by us vitrificated solvents all investigated macromolecules at 77K have conformations of Gauss ball. This result at first glance is seemed to be surprising enough, since various systems were studied. However, we should take into account that here we determined conformational state of macromolecules modified by spin markers. Moreover, the quality of solvent depends on temperature and probably θ-temperature of solutions of spin-marked polymers in used solvents is insignificantly differed from vitrification temperatures of these solvents. The conclusion that macromolecules of spin-marked PVP and PMAA in non-marked polymer have conformation of Gauss ball corresponds to Flory's theory about macromolecules conformations in undiluted amorphous polymers [5] and also to experimental data on determination of macromolecules conformation in solid amorphous state by method of neutron scattering [7].

EPR-Spectroscopy of Complex Polymer Systems

Scheme 1. Spin-marked macromolecules.

131

132

A. M. Wasserman and M. V. Motyakin Table 1. Conformational characteristics of spin-marked macromolecules at 77K

œ

Number of system

Polymer

Molecular mass

β,œ mole %

1

PVP*-1

5·104

17

2

PVP*-1

5·104

3

PVP*-1

4

α, Å

1/2, Å

methanol

10

220

17

n-propanol

9

200

5·104

17

PVP

11

240

PVP*-1

5·104

9

methanol

10

220

5

PVP*-2

1,4·105

20

ethanol

10

360

6

PVP*-2

1,4·105

20

PVP

9,5

350

7

PVP*-2

1,4·105

8,5

ethanol

9

330

8

PVP*-1

1·106

10,5

methanol

11

1070

9

PVP*-1

1·106

10,5

PVP

10

980

10

PMAA*

1,4·105

23

methanol

11

440

11

PMAA*

1,4·105

23

PMAA

12

380

12

PMAA*

1,4·105

23

methanol

12

480

13

PMAA*

1,4·105

23

methanol (60 mass %)−water

13

520

14

STMAL*

6·104

12

dimethylforma mide

9

220

Solvent

Mole content of spin markers on polymer chain

The values of mean-square length of monomer unit and distance between polymer chain ends are presented in Table 1. It is important to pay attention to the fact that sizes of macromolecule ball in vitrificated low-molecular solvents and in solid non-marked polymer are differed insignificantly. When the salt of PMAA is formed the rigidity of polymer chain is increased a little that leads to little increase of values of mean-square length of monomer unit and distance between polymer chain ends. The result obtained under addition to polymer salt solvent in methanol (40 vol. % of water, at large content of water the solution is not vitrificated, but is crystallized) represents special interest; at that the macromolecule in solid state keeps conformation of Gauss ball (Figure 2), however, as we should expect, rigidity (parameter α) and sizes of ball are increased (Table 1). Presented here results allow making conclusion that method of EPR-spectroscopy of spin markers is effective method of determination of macromolecules conformation in solid state. This method may significantly enlarge information obtained by other methods, in particular by method of neutrons scattering. The advantage of this method is in the fact that it may give information about conformational state of comparatively small parts of solid polymers chains.

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The disadvantage of the method is that as a rule it requires significant modification of polymer chain as a result of introduction of essential number of spin markers. Introduction of markers may change polymer properties. However, this disadvantage may be removed by the use of modern impulse methods of EPR-spectroscopy (see for example [14,15]) which are more sensitive to dipole-dipole interaction of uncoupled electrons than traditional methods of EPR-spectroscopy.

2. MOLECULAR DYNAMICS AND ORGANIZATION OF COMPLEXES POLYELECTROLYTE−DETERGENT Method of EPR-spectroscopy of spin markers and probes turned to very informative under investigation of self-associating polymer systems, in particular complexes of polyelectrolytes with surface active substances (SAS). Application of this method allowed establishing of particularities of molecular dynamics and local organization of SAS molecules, and also segment mobility of macromolecules in such complexes [16-26]. The interest to complexes is caused by various reasons. Firstly, it is a novel class of polymer materials possessing unusual physical-chemical properties. Moreover, possible application of such complexes for solution of practically important problems is of great interest, for example as sorbents for removal of toxic substances from water mediums, for purposeful transport of medicines in organism, etc. (see for example [27]). There are complexes of polyelectrolytes with ionic and nonionic SAS. In the first case formation of micelles occurs on polymer chain that may lead to both the change of conformation and segment mobility of macromolecules and to the change of aggregation number and local organization of micelles included into the complex. In the second case as a rule the numbers of micelles aggregation included into complex and "free" micelles are practically not differed, however, under formation of complex macromolecule conformation and local mobility of detergents molecules may be significantly changed. The results of investigation of molecular dynamics and organization of complexes obtained by EPRspectroscopy method of spin markers and probes will be considered below.

2.1. Complexes of Linear Polyelectrolytes with Ionic SAS 2.1.1. Molecular Dynamics and Organization of Complexes Micellar Phase Usually they distinguish two types of complexes polyelectrolyte−ionic SAS. Firstly, complexes in which only the part of polymer units is connected with SAS iones. Such complexes are soluble in water; their solubility is determined by the presence of polymer units not connected with SAS ions. Secondly, the complexes in which all or almost all units of polymer chain are connected with SAS ions. Such complexes are insoluble in water and are precipitated. Schematically soluble and non-soluble complexes of polyelectrolyte−SAS (on the example of complexes of polycarbonic acids with alkyltrimethylammonium bromides) are presented in Figure 3.

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A. M. Wasserman and M. V. Motyakin

A

B

Figure 3. Macromolecular organization of soluble (a) and non-soluble (b) complexes of polycarbonic acids with alkyltrimethylammonium bromides.

The particularities of molecular dynamics and local organization of micellar phase of complexes were formulated on the example of complexes of polyacrylic (PAA), polymethacrylic (PMAA) acids and polystyrenesulfonate (PSS) with dodecyl- (DTAB), tetradecyl- (TTAB and cetyltrimethylammonium (CTAB) bromides, and also of poly-N,N'dimethyldiallylammonium chloride (PDAC) and poly-N-ethyl-4-vinylpyridinium bromide (PEVP) with sodium dodecylsulfate (SDD) (formulas of polymers are presented in Scheme 2).

Scheme 2.

Particles of complexes of PAA and PMAA with alkyltrimethylammonium bromides include one macromolecule and micellar phase is formed as one "big" micelle (Figure 3). complexes of PSS are also formed in the volume of one macromolecule, however in contrast to complexes of polycarbonic acids micellar phase is formed as "not big" aggregates [28]. Quite the contrary, the particles of complexes of PDAC with SDD are consisted of dozens of

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135

polymer macromolecules and dozens of thousands of SAS ions [29]. Macromolecular organization of complexes of PEVP with SDD depends on polymer molecular mass: complexes on the base of PEVP with polymerization degree Pw = 1000 represent strongly associated particles including not less than 50 macromolecules and 2500 ions of SDD, whereas particle of complexes on the base of PEVP Pw = 2000 includes one macromolecule and approximately 500 ions of detergent [30]. General regularities of molecular dynamics and local organization of micellar phase of polyelectrolytes complexes with ionic SAS [16-22, 26] were formulated; for the solution of this problem spin probes were used. Formulas of some of the last ones are presented in Scheme 3. CH3(CH2)17-n

(CH2)n-2COOH

C

O

N

O

N

O

N C2 H5

R2

n=5 (5DSA); n=16 (16DSA) O

. O

N

N

N CH2

N C6H13

C

R2’

CH

R4’

Scheme 3. Formulas of spin probes.

According to our opinion usage of spin probes of various structures allows obtaining of the information about various parts of micellar phase of complexes. Probe 5DSA is built into micellar phase in such way that carboxyl group is situated close to interface, whereas paramagnetic fragment is localized deeper, on the distance of 5-7Å from interface [31]. Probe 16DSA in complex micelle as a rule takes on relatively "elongated" conformation in which paramagnetic fragment is localized near the "nucleus" of micelle (in contrast to "free" micelles in which probe molecule takes on U-shaped conformation and paramagnetic fragment is situated close to charged groups of SAS) [32]. Paramagnetic fragments of probes R2, R2' and R4' are situated close to interface; these are relatively "big" probes which give "averaged" information about molecular mobility of micellar phase. When analyzing experimental EPR spectra of spin probes in micellar phase of complexes we used the model "Microscopic Order and Macroscopic Disorder" (MOMD) [33]. This model is often used for description of EPR spectra of spin probes in micelles, dispersions, vesicles and other microscopically ordered but macroscopically disordered systems [34, 35]. The parameters of model are: −

the main values of tensor of ultrafine interaction and g-tensor of nitroxyl radical;

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A. M. Wasserman and M. V. Motyakin −

− −

coefficients of rotational diffusion of spin probe in relation to axes perpendicular (R⊥) and parallel (R||) to main axes of molecular rotation. Average time of correlation τ, is connected with coefficients of rotational diffusion by the ratio: τ = 1/6Rav, where Rav = (R⊥2 · R||)1/3. angle β between directions of main axes of diffusion tensor and tensor of ultrafine interaction (or g-tensor); parameter of order S, which depends on orientational potential and is determined by the ratio S = ½ < 3cos2θ − 1 >, where θ − the angle between anisotropy direction of medium and long axis of pin probe symmetry (for more details see [33, 36]); this parameter characterizes degree of order (local organization) of micellar phase of complexes.

The following results were obtained: 1. Rotational mobility of spin probes in micellar phase of polymer complexes is significantly lower than in "free" micelles. This is general regularity which is observed for all studied complexes with the use of various spin probes. As an example in Figure 4 we compare EPR spectra of probes 5DSA and 16DSA in "free" micelles of SDD and in complexes PEVP−SDD; it is obvious that these spectra are strongly differed. These results allow unambiguous concluding that mobility of spin probe in complex is significantly lower than in "free" micelle. This result is not surprising and is explained by the fact that interaction of SAS molecules with polymer chain in complex leads to significant decrease of local mobility of detergent molecules. It is important to mark that local mobility of detergent molecules in micellar complex depends on a lot of factors such as interaction polymer−detergent, segment mobility of macromolecules, length of hydrocarbon part of detergent molecule, etc. and it may be significantly differ for various complexes (for details see [22]). 2. Micellar phase of complexes polyelectrolyte−detergent near the charged SAS groups is highly organized molecular system. This conclusion is made on the base EPR-spectra analysis of probe 5DSA, paramagnetic fragment of which is localized on the distance 57 Å from interface. The values of order parameter (S) of probe 5DSA in some organized molecular systems, including micellar complexes polyelectrolyte−SAS are presented below. In "free" micelles of SDS the value of S is equal to 0,3-0,37 [31], in SDS mono-layers localized on the surface of oil emulsion in water it is 0,45–0,48 [31, 35], in vesicles of dioctodecyldimethylammonium chloride − 0,6 [34], phospholipids membranes − 0,65-0,68 [37]. In complexes polyelectrolyte−SAS the values of S are equal to: PAA−DTAB, 0,44-0,46 PAA−TTAB, 0,48-0,50, PAA−CTAB − 0,55-0,56, PSS−DTAB 0,42-0,52, PSS−TTAB 0,44-0,56, PSS−CTAB 0,58-0,62, PDAC−SDD 0,61-0,62 [22], PEVP−SDD 0,62 [26]. Thus, by the level of molecular organization at least in the place of localization of paramagnetic fragment of probe 5DSA, micellar phase of complexes polyelectrolyte−SAS significantly exceeds "free" micelles and approaches to phospholipids membranes. 3. Parameter of order and correlation time of probe rotation are increased with increase of length of hydrocarbon part of detergent molecule. This is a general regularity. For

EPR-Spectroscopy of Complex Polymer Systems

137

example, correlation times of probe 5DSA rotation in micellar phase of polystyrenesulfonate complexes with alkyltrimethylammonium bromides are equal to: for system PSS-DTAB 1,9⋅10-9 sec, for PSS-TTAB 2,4⋅10-9 sec, for PSS-CTAB 3,2⋅10-9 sec [22]. Presented result demonstrates the role of hydrophobic interactions in formation of micellar phase of complexes polyelectrolyte−SAS. 4. Far from interface, close to micelle "site" (in that place where paramagnetic fragment of probe 16DSA is localized) molecular order of micellar phase of complexes is significantly lower, than near the interface. Obviously, far from interface hydrocarbon "tails" of detergents molecules are curved, entangled and form the medium which properties are insignificantly differed from isotropic. 5. Molecular mobility and order parameter of spin probes in soluble and insoluble complexes practically are not differed. This important result was obtained under investigation of complexes of PAA, PMAA with alkyltrimethylammonium bromide and also of complexes PDAC and PEVP with SDD with the use of various spin probes. This result means that local organization of micelle formed in soluble complexes is practically not changed under formation of insoluble complexes (see Figure 2). 6. Under transition from molecular-disperse complexes PEVP−SDD (Pw = 2000) to aggregated (Pw = 1000) differences in EPR-spectra of various spin probes were not observed [26]. Local organization and local dynamics of micellar phase of complexes don't undergo any noticeable changes at very significant reduildings of macromolecular structure of complexes in solution. Under the influence of polymer chains of various molecular masses the complexes of various sizes, structure and macromolecular organization may formed, however elementary sections of micellar phase of which complex is consisted remain practically unchangeable.

1

1

2

2 '

2A ll

3

3

20 ГС

20 ГС

'

2A l (app)

A

B

Figure 4. EPR-spectra of spin probes 5DSA (a) and 16DSA. 1 − SDD micelles, [SDD]=0,03 mole/l; complexes PEVP−(Pw=1000)−SDD: 2 − soluble complexes, 3 − insoluble complexes. Firm line presents experimental spectra, dotted line presents calculated spectra.

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A. M. Wasserman and M. V. Motyakin

2.1.2. Segment Mobility of Macromolecules in Complexes The influence of complex formation on segment mobility of polymer chains was studied on the example of PMAA complexes with DTAB, TTAB and CTAB [19], and also PEVP complexes with SDD [26]. The formula of spin-marked PMAA (PMAA*) is presented in Scheme 1; formula of spin-marked PEVP (PEVP*) is presented in Scheme 4. Content of spin marks in the case of PMAA was mark per 30 units, in the case of PEVP 1 mark was per 100 macromolecules.

CH2

CH2

CH

1% J

C2H5

CH

N

N

N CH2

CH2

CH

84%

15%

Br

C O

NH N O

Scheme 4. Formula of spin-marked PEVP*.

When determining segment mobility of spin-marked macromolecules we used the model according to which spin mark participated in two types of motion: slow isotropic rotation together with segment of macromolecule with effective correlation time τsegm and fast vibration (vibration angle α) in relation to macromolecule segment with correlation time τ1 << τsegm (the model of fast scillations of nitroxyl) [38, 39]. The examples of EPR-spectra of spin-marked PMAA in water solution and also in soluble and insoluble complexes PMAA−DTAB are presented in Figure 5. Conformation of PMAA macromolecule depends on solution pH [40, 41]. In acid mediums PMAA macromolecules are in "compact" conformation, stabilized by system of hydrogen bonds between nonionic carboxyl groups. Increase of ionization degree of macromolecule leads to decomposition of hydrogen bonds and at pH > 7 macromolecule takes conformation of swollen statistical ball. Change of macromolecule conformation with change of pH is caused by the action of electrostatic repulsion forces between likely charged carboxyl groups. Change of pH leads to sharp change of EPR-spectrum of spin-marked PMAA* (Figure 5): transition of PMAA* macromolecule from compact conformation (pH=6) into conformation of swollen ball (pH=9) is accompanied by the growth of segment mobility ad angle of fast vibrations of nitroxyl. On the base comparing of EPR experimental spectra with ca;lculated ones the values of τsegm and α were determined. In compact conformation τsegm=80nsec, and α=66°, in conformation of swollen ball they are segm=20nsec, and α=100°.

EPR-Spectroscopy of Complex Polymer Systems

139

Formation of complex PMAA* with DTAB at pH=6 leads to significant changes of EPR spectra, segment mobility of PMAA* and amplitude of nitroxyl vibrations in complex (τsegm=20nsec, and α=98°) are significantly higher than for PMAA* in water solution at the same conditions and are insignificantly differed from corresponding values for PMAA* solution at pH=9. on the base of these results we may unambiguously conclude that under formation of complex PMAA*−DTAB the compact structure of PMAA is destructed that is accompanied by increase of segment mobility of macromolecule and side groups vibrations amplitude.

Figure 5. Experimental (firm line) and calculated (dotted line) EPR-spectra of spin-marked PMAA (PMAA*) and complexes PMAA*−DTAB in solution. 1 − PMAA*, pH=6; 2 − PMAA*, pH=9; 3 − soluble complex pH=6, Z=0,2; 4 − soluble complex pH=9, Z=0,2; 5 − insoluble complex pH=9, Z=1,0. Z is the ratio of mole concentrations of SAS ions and carboxyl groups in system.

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A. M. Wasserman and M. V. Motyakin

In alkali mediums at pH=9 where macromolecule is in conformation of swollen ball formation of water-soluble complexes doesn’t lead to noticeable change of segment mobility; EPR-spectrum of soluble in water complex PMAA*−DTAB is slightly differed from PMAA* spectra at pH=9 and complex's EPR-spectra at pH=6 (Figure 5). Experimental EPR-spectrum of complex PMAA*−DTAB at pH=9 is satisfactorily agreed with theoretical one, calculated with the use of almost the same parameters (τsegm=20nsec, and α=98°) used for modelling of water solution of PMAA* at pH=9 and complex PMAA*−DTAB at pH=6. Thus, segment mobility of PMAA* in soluble complexes PMAA*−DTAB is practically independent from solution pH and is insignificantly differed from PMAA* segment mobility in water solution at pH=9. One may assume that life time of single salt bond PMAA−DTAB is significantly lower than correlation time of segment motions of macromolecule and that is why formation of such bonds practically doesn’t influence on segment mobility of macromolecule. Under formation of insoluble in water complexes in which all ionic groups of PMAA are connected by salt bonds with SAS ions the sharp change of spectrum of spin-marked macromolecule is observed (Figure 5, spectrum 5). While modelling this spectrum we assume that τsegm=∞, and α=84°. In other words segment mobility of macromolecule in insoluble complex PMAA*−DTAB is strongly limited, whereas local mobility of side groups is high enough and is insignificantly differed from mobility of side groups in soluble complexes. Obviously in given case transition from soluble to insoluble complexes is accompanied by sharp increase of local concentration of macromolecules units whereas packaging density of SAS ions in micellar phase is practically not changed.

1

2

3

4

5

6

Figure 6. Experimental (firm line) and calculated (dotted line) EPR-spectra of spin-marked PEVP* (Pw=1000) in solution (1) and in complexes PEVP*−SDD at various mole ratios Z = [SAS]/[PEVP]: Z = 0,1(2); Z=0,2(3); Z = 0,3(4); Z =0,4(5); Z=1,0(6).

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141

Experimental and calculated EPR-spectra of spin-marked PEVP* in solution and also in soluble and insoluble complexes with SDD (details of calculation are presented in [26]) are presented in Figure 6. It is important to note, that EPR-spectra of all soluble complexes are the superposition of spectrum of "free" polymer in solution (Figure 6, spectrum 1) and polymer spectrum in insoluble complex (Figure 6, spectrum 6). This fact means that in given case (in contrast to complexes PMAA*−DTAB) the segment mobility of macromolecule units participating in complex formation remains constant under transition from soluble to insoluble complexes. Moreover, segment mobility of free sections of macromolecule not participating in complex formation is not changed as a result of complex formation. As a result of modelling the following values were obtained: − −

for polymer in solution τsegm(1)=9,7nsec, and α=100°; for polymer in complex τsegm(2)=25nsec, and α=75°.

Thus, in dependence on the way of macromolecule conformation change, ratio of life times of salt bonds and correlation time of macromolecule segment rotation, change of local macromolecule units density, under formation of complex polyelectrolyte−SAS segment mobility of macromolecule may be increased, decreased or remains constant.

2.2. Complexes of Linear Polyelectrolytes with Nonionic SAS Polyacids complexes (for example polyacrylic and polymethacrylic) with nonionic SAS on the base of polyethyleneglycol (PEG) are formed in water solutions at the expense of hydrogen bonds between non-dissociated carboxyl groups of polyacid and hydrogen atoms of PEG [42, 43]. At small concentrations of SAS in solution but higher than critical concentration of micelle formation (CCM) the decrease of sizes (compacting) of polymer ball occurs. Further increase of detergent content in solution leads to increase of polymer ball sizes. Observing particularities are explained by the fact that at low concentrations of SAS the complex is formed in which PEG groups of detergent molecules are connected mainly by hydrogen bonds with hydroxyl groups of polyacid. With the rise of SAS content in solution rebuilding of complex structure occurs, the associate is formed in which considerable part of PEG groups is free, not connected with macromolecule by hydrogen bonds [44]. Proposed structures of compact and swollen states of complex are presented in Figure 7. Let consider regularities of molecular dynamics of micellar phase of complexes polyacid−SAS on the example of PMAA complexes with dodecylsubstituted polyethylene glycol (DD-PEG, formula is presented below) [22, 23]. Analogous regularities were observed under investigation of PAA complexes with DD-PEG [24]. СН3(СН2)11- О – (СН2СН2О)38-Н DD-PEG

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Figure 7. Hypothetic structure of complex of polycarbonic acid with dodecylsubstituted polyethyleneglycole at low (compact ball) (a) and high (swollen ball) (b) contents of detergent in solution.

The examples of EPR-spectra of probes 5DSA (its formula is in Scheme 3) and R15 (the formula is presented below) at various mass ratios of components φ = [DD-PEG] : [PMAA] but at constant PMAA concentration (0,3 g/dl) are presented in Figure 8; in all cases SAS concentration in solution was significantly higher than CCM. It is reasonable to assume that as well as in other micellar systems the paramagnetic fragment of probe 5DSA is localized in micelle nucleus whereas of R15 probe it is close to interface:

C 15 H31CONH

.

N O

R15 EPR-spectrum of probe 5DSA in polymer complex at low content of detergent (at φ=0,5) is sharply differed from spectrum 5DSA in "free" micelle (Figure 8a). Correlation times of probe rotation (τ) calculated by model of isotropic rotation are equal to 1,8⋅10-8sec in polymer complexand to 1,9⋅10-9sec in free micelle. Formation of polymer complex is accompanied by sharp decrease of local molecular mobility of micellar phase caused by interaction of detergent molecules with polymer chain. Under the rise of detergent content up to φ=4 EPRspectra of spin probe are practically not changed. This fact means that "free" micelles are absent in system and local mobility of micellar phase in the place of localization of paramagnetic fragment of spin probe for complexes with structure φ ≤ 4 is differed insignificantly. At φ = 5 changes in spectrum are observed which may be caused for example by rebuilding of complex structure. It is not excluded however that at φ = 5 "free" micelles may be formed in the system. At φ = 10 the amount of "free" micelles is so large that EPR spectra of probe in micellar system in the presence and absence of PMAA are practically not differed.

EPR-Spectroscopy of Complex Polymer Systems

A

143

B

Figure 8. EPR spectra of spin-probe 5DSA (a) in "free" micelles DD-PEG and in the system PMAA-DDPEG at various mass ratios (φ) of components in water solution of PMAA (0,3g/dl).

Under the use of spin probe R15 more complex picture is observed. At φ = 0,5 EPRspectrum of spin probe is the superposition of spectra of spin probes and their correlation times are noticeably differed (τ1= 9·10-9sec, relative part of such probes is χ=90%, τ2=1,4·109 sec, χ=10%). In "free" micelle correlation time of probe R15 rotation is equal to 7⋅10-10 sec. these result confirm the conclusion that local mobility of detergent molecules in micelle phase of complex is significantly lower than in "free" micelle. Observing superposition of spectra is caused by dynamic micro-heterogeneity of micellar phase and allows concluding that local mobility of various parts of micellar phase of complex (where paramagnetic fragment of probe is localized) is noticeably differed. Obviously, the probes rotating relatively "slow" are localized near the detergent molecules connected by hydrogen bond with polymer chain, whereas probes rotating "fast" are situated near the detergent molecules which polyethyleneglycol groups are free and not bonded with polymer chain (Figure 7). Under the rise of SAS content in system for example at φ=1 correlation times of probes rotation localized in differing in mobility parts of complex micellar phase are practically not changed (τ1= 9·0-9sec, τ2=1,4·10-9sec), whereas relative part of probes rotating fast is increased up to 25%. Probably under the rise of micelle amount in system the part of detergent molecules in micellar complex not bonded with macromolecule (Figure 7) and consequently probes part rotating "fast" are increased. This regularity is observed also with further increase of detergent content in the system. So, at φ>1 superposition of spectra is not observed, however correlations times of probe rotation are monotonously decreased with the rise of SAS content in solution. Correlation times are equal to: at ϕ = 2, τ=3,5·10-9sec, at ϕ =3, τ=3·10-9sec, at ϕ =4, τ=2,6·10-9sec. It is important to mark that all observing particularities of spectra are connected with the change of local mobility of detergent molecules caused by rebuilding of

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complex structure. At φ=5 appearance of free micelles in system is possible and at ϕ = 10 their amount is so large that spectra of probe in micellar system in the presence and absence of polymer are practically not differed. Obtained results allow formulating general regularities of molecular dynamics of detergent molecules in micellar phase of polyacids complexes with nonionic SAS. Local mobility of detergent molecules in polymer complexes is significantly lower than in "free" micelles. This fact is caused by formation of hydrogen bonds between for example PEG groups of SAS molecules and non-dissociated carboxyl group of polyacid. In complex local mobility of SAS molecules connected with polymer chain is significantly lower than mobility of detergent's molecules not connected with macromolecule. With the rise of micelles amount the part of SAS molecules is increased in complex, which PEG groups are free and not bonded with polymer chain. As a result mobility of detergent's molecules in complex micellar phase is increased.

3. EPR-TOMOGRAPHY OF POLYMERS DESTRUCTION REACTION In the department managed by N.M. Emanuel they showed by the method of spin probe that during thermo-oxidation process the process leading to both polymer destruction and structuring might proceed. So, for example at the first stages of polyorganosiloxane oxidation on air at high temperatures destruction process occurs as a result of which low-molecular products are formed. Plasticizing action of low-molecular products leads to increase of segment mobility of polymer regusted by method of EPR-spectroscopy of spin probe. At deep stages of oxidation processes of structuring and polymer chains grafting proceed as a result of which segment mobility is sharply decreased [1, 45]. Method of EPR-tomography developed in the Institute of Chemical Physics of RAS [46] allows both detecting of molecular mobility and its change at thermo- or photo-destruction of polymer in various points of sample and registration of the distribution of oxidation active sites through the sample. This method allows identification of polymers parts in which destruction process proceeds. Solution of this problem is of great importance for selection of conditions of polymer materials exploitation. Developed in works [47-50] idea of application of EPR-tomography method for investigation of polymers destruction processes lies in the following. Hindered amine which formula is presented below is introduced into polymer. As a result of amine reaction with peroxide radicals formed during polymer oxidation process (Scheme 5) stable nitroxyl radicals are formed. Nitroxyl radicals may be formed only at those parts of polymers where there are peroxide radicals, i.e. process of thermo-oxidative (or photooxidative) destruction proceeds. Then one determines spatial distribution of nitroxyl radicals through the sample and so, it becomes possible to identify those regions of polymer in which oxidation reaction proceeds. Let consider two examples. In works [46-48] by method of EPR-tomography thermo- and photo-oxidation of poly(acrylonitrile-butadiene)styrene (ABS) copolymer were studied. This polymer is structurally and dynamically micro-heterogeneous, i.e. there are regions with high content of polybutadiene and regions with high content of polystyrene or polyacrylonitrile. In polymer

EPR-Spectroscopy of Complex Polymer Systems

145

the EPR-spectrum of nitroxyl radical resulted from hindered amine by Scheme 5 is the superposition of spectra of radicals rotating "fast" (in regions enriched by polyburtadiene) and "slow" (in regions enriched by polystyrene or polyacrylonitrile) (the inset in Figure 9).

O H

N

O

OC(C H2)8C O

N

H

P NH

POO

NO POOP

NOP POO

Scheme 5. Reactions of spatially hindered amines (see formula) with peroxide radicals.

Distribution of concentration of nitroxyl radicals resulted from hindered amine in the process of ABS-copolymer thermo-oxidative destruction through the sample thickness (concentration profile) is presented in Figure 9a. It is obvious that maximum concentration of nitroxyl is observed near the surface of sample. This fact means that in given case process of destruction proceeds mainly near the surface; in the middle of sample the process of oxidative destruction practically doesn't proceed. We should note that under oxidation namely in those regions of sample where process is the most intensive the EPR-spectrum of nitroxyl radical is changed: relative part of radicals rotating "fast" is decreased [46-48]. Consequently, during oxidation process the grafting of polymer chains occurs in regions enriched by polybutadiene; as a result segment mobility of macromolecules is decreased and consequently the rotational mobility of spin probes localized in these reasons. Concentration profile of nitroxyl radicals resulted from thermo-oxidative destruction of other polymer − ethylene copolymer with propylene is presented in Figure 9b. In this case maximum concentration of nitroxyl radicals is observed not on the borders but in the center of sample: the process of thermo-oxidative destruction proceeds mainly in sample depth [49]. We shall not carry out kinetic analysis of obtained results in this work; we shall only notice that EPR-spectroscopy is more sensitive method for polymers destruction investigation than traditional methods such as method of IR-spectroscopy [47, 50]. Presented in this work results allow concluding that method of EPR-tomography is perspective and very promising method of investigation of polymers destruction processes.

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3300

3320

3340

3360

3380

3400

Магнитное поле, Гс

0,0

0,5

1,0

1,5

2,0

2,5

3,0

3,5

4,0

a

thickness, mm

0,0

0,5

1,0

1,5

2,0

2,5

3,0

3,5

b

thickness, mm Figure 9. Distribution of nitroxyl radicals concentration by thickness of sample underwent thermo-oxidative destruction at 120°C: a − poly(acrylonitril-butadiene-styrene (ABS) copolymer), thickness of sample is 3,8mm; b − polypropylene copolymer with polyethylene, thickness of sample is 3,4mm. The inset is the example of EPR-spectrum of nitroxyl radical in ABS-copolymer.

REFERENCES [1] [2] [3]

N.M. Emanuel, A.L. Buchachenko, Chemical physics of polymers ageing and stabilization, Moscow: Nauka (1982) (in Russian). A.M. Wasserman, A.L. Kovarsky, Spin marks and probes in polymers physical chemistry, Moscow: Nauka (1986) (in Russian). A.M. Wasserman, Spin Labels and Spin Probes in Polymers. In Book: Electron Spin resonance, 15, London: The Royal Society of Chemistry (1996).

EPR-Spectroscopy of Complex Polymer Systems [4] [5] [6] [7] [8] [9] [10] [11] [12] [13]

[14] [15] [16] [17] [18] [19] [20] [21] [22] [23] [24] [25] [26] [27] [28] [29]

147

M.V. Vol'kenstain, Configuration statistics of polymer chains, Moscow, Leningrad (1959) (in Russian). P. Flory, Statistical mechanics of chain molecules, Moscow (1971) (in Russian). De Zhenn P., Idea of scaling in polymers physics, Moscow (1982) (in Russian). D.M. Sadler, in Comprehensive Polymer Science, Eds. C.Booth and C.Price, Oxford (1989). K.A. Peterson, A.D. Stein, M.D. Fayer, Macromolecules, 23, 111 (1990). T.N. Khazanovich, A.D. Kolbanovsky, A.I. Kokorin, T.V. Medvedeva, A.M. Wasserman, Polymer, 33, No.24, 5208 (1992). A.M. Wasserman, A.D. Kolbanovsky, A.I. Kokorin, T.V. Medvedeva, T.N. Khazanovich, Vysokomol. Soed., 34A, No.10, 75 (1992) (in Russian). A.Yu. Grosberg, A.R. Khokhlov, Statistical physics of macromolecules, Moscow: Nauka (1989) (in Russian). A.I. Kokorin, K.I. Zamaraev, Biofizika, 17, No.1, 34 (1972) (in Russian). A.M. Wasserman, T.N. Khazanovich, New Frontiers in Spin Probe and Spin Label SPR Spectroscopy of Polymers. In Polymer Yearbook, Hardwood Academic Publishers, 12, 153 (1995). A.D. Milov, A.G. Matyasov, Yu.D. Tsvetkov, Appl. Magn. Res., 15, 107 (1998). A.D. Milov, Yu.D. Tsvetkov, F. Formaggio, et al, Phys. Chem., Chem. Phys., 6, No.13, 3559 (2004). A.M. Wasserman, Yu.A. Zakharova, M.V. Motyakin, V.A. Kasaikin, L.A. Krinitzkaya, Vysokomol. Soed., 37B, 1561 (1995) (in Russian). А.М. Wasserman, T.N. Khazanovich, V.A. Kasaikin, Appl.Magn. Res., 10, 413 (1996). V.A. Kasaikin, Yu.A. Zakharova, M.V. Motyakin, A.M. Wasserman, Kolloid. Zh., 58, 454 (1996) (in Russian). A.M. Wasserman, Yu.A. Zakharova, M.V. Motyakin, V.A. Kasaikin, et. al., Vysokomol. Soed., 40A, 942 (1998) (in Russian). V.A. Kasaikin, A.M. Wasserman, J.A. Zakharova, M.V. Motyakin, Colloids and Surfaces, 147A, 169 (1999). Yu.A. Zakharova, M.V. Otdel'nova, I.i. Aliev, A.M. Wasserman, V.A. Kasaikin, Kolloid. Zh., 64, 170 (2002) (in Russian). A.M. Wasserman, V.A. Kasaikin, Yu.A. Zakharova, et. al., Spectrochimica Acta, 58A, 1241 (2002). L.L. Yasina, I.I. Aliev, A.M. Wasserman, V.Yu. Baranovskii, Vysokomol. Soed., 44А, 1017 (2002) (in Russian). V. Doseva, L.L. Yasina, I.I. Aliev, A.M. Wasserman, V.Yu. Baranovskii, Kolloid. Zh., 65, 1 (2003) (in Russian). A.M. Wasserman, L.L. Yasina, I.I. Aliev, V. Doseva, V.Yu. Baranovsky, Colloid. Polym. Sci., 282, 402 (2004). A.M. Wasserman, M.V. Otdel'nova, Yu.A. Zakharova, M.V. Motyakin, et. al., Khimicheskaya fizika, 24, No.3, 29 (2005) (in Russian). E.D. Goddard, K.P. Ananthapadmanabhan (Eds), Interaction of Surfactants with Polymers and Proteins, London: CRS Press (1993). E.B. Abuin, J.C. Scaiano, J. Am. Chem. Soc., 106, 6274 (1984). V.A. Kasaikin, E.A. Litmanovich, A.B. Zezin, V.A. Kabanov, Dokl. RAN, 367, 359 (1999) (in Russian).

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[30] M.V. Otdel'nova, Yu.A. Zakharova, E.M. Ivleva, et. al., Vysokomol. Soed., 45A, 1524 (2003) (in Russian). [31] V.A. Livshitz, B.G. Dzikovskii, Zh. Fiz. Khimii, 68, 1650 (1994) (in Russian). [32] A.M. Wasserman, Uspekhi khimii, 63, No.5, 391 (1994) (in Russian). [33] D.E. Budel, S. Lee, S. Sexana, J.H. Freed, J. Magn. Res., 120, 155 (1996). [34] P.J. Brat, L. Kevan, J. Phys. Chem., 96, 6849 (1992). [35] B.G. Dzikovski, V.A. Livshits, Phys. Chem. Chem. Phys., 5, No.23, 5271 (2003). [36] D.J. Schneider, J.H. Freed, Calculation slow motional magnetic resonance spectra, in L.J. Berliner, J. Reuben (Eds.) Biological Magnetic Resonance, 8, New York: Plenum Press (1989). [37] M.D. Reboiras, D. Marsh, Biochem. Biophyc. Acta Biomemr., 1063, 259 (1991). [38] V. Timofeev, B. Samarianov, Appl. Magn. Res., 4, No.4, 523 (1993). [39] V. Timofeev, B. Samarianov, J. Chem. Soc. Perkin Trans II., 1345 (1995). [40] B. Bednar, H. Moravetz, J.A. Shafer, Macromolecules, 10, 1940 (1985). [41] J. Pilar, J. Labsky, Macromolecules, 24, No.14, 4188 (1991). [42] S. Saito, T. Tanigichi, Kolloid. Z., 248B, 1039 (1971). [43] A.D. Antipina, V.Yu. Baranovskii, A.M. Papisov, V.A. Kabanov, Vysokomol. Soed., 14A, 941 (1972) (in Russian). [44] V.Yu. Baranovskii, V. Doseva, S. Shenkov, Kolloid. Zh., 57, No.3, 293 (1995) (in Russian). [45] A.L. Kovarskii, S.M. Mezhikovskii, A.M. Wasserman, Vysokomol. Soed., 15А, No.3, 650 (1973) (in Russian). [46] O.E. Yakimchenko, A.I. Smirnov, Y.S. Lebedev, Appl. Magn. Reson., 1, 1 (1990). [47] M.V. Motyakin, S. Schlick, Polymer Degradation and Stability, 76, 25 (2002). [48] M.V. Motyakin, J.L. Gerlock, and S. Schlick, In Mallinson L.G. (Ed.) Ageing Studies and Lifetime Extension of Materials, New York: Kluwer Academic/Plenum Publishers (2001). [49] M.V. Motyakin, S. Schlick, Macromolecules, 35, 3984 (2002). [50] M.V. Motyakin, Abstracts of “Modern Development of Magnetic Resonance”, Kazan, August 15-20, 83 (2004) (in Russian).

In: Chemical and Biochemical Physics: New Frontiers ISBN 1-60021-165-8 Editor: G. E. Zaikov, pp. 149-165 © 2006 Nova Science Publishers, Inc.

Chapter 14

ORGANOSILICON COPOLYMERS WITH CARBOCYCLOSYLOXANE FRAGMENTS IN DIMETHYLSILOXANE BACKBONE O. Mukbaniani*1, G. Zaikov2, N. Mukbaniani1 and T.Tatrishvili1 1

2

I.Javakhishvili Tbilisi State University, Tbilisi, Georgia Institute of Biochemical Physics, Russian Academy of Sciences, Moscow, Russia

INTRODUCTION Nowadays the reactions of hydride polyaddition are in a great use in siliconorganic chemistry. Recently a great importance is paid to this reaction in the field of obtaining complicated monomers [1] and also in the field of investigation the mechanisms of additions on the various catalyst systems Pt, Pd, Co, carbonyl of metals and investigation of specificity of actions of various catalytic systems [2-5]. From literature it’s known, that introduction of cyclic fragments in dimethylsiloxane chain is resulted in variation of the spiral-shaped structure of dimethylsiloxane polymers, which causes variation of their physical and chemical properties [6]. For the purpose of increasing the thermal-oxidative stability of siliconorganic polymers a great importance is paid to the method of synthesis of functional group containing organocyclosiloxanes and to the methods of modification of linear siloxane chains by single or condensed cyclic fragments by using reactions of hydride polyaddition. Besides HFC reaction of preliminarily prepared cyclic organosiloxanes with functional groups and difunctional organosilicon compounds, which give an opportunity to preserve cyclic groups in the polymeric backbone, hydride polyaddition is also widely used, which proceeds under soft conditions and does not involve cyclic structures, introduced into the backbone [7-9]. The synthesized carbosiloxane copolymers with disilylethylene groups in the main chain possess less thermal-oxidative stability in comparison with polyorganosiloxane analogues, but they have greater thermal stability at the absence of oxygen [9].

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Reviewed in this paper is synthesis of cyclolinear carbosiloxane copolymers with regular disposition of mono-, bi- and tricyclic fragments in dimethylsiloxane backbone using hydride polyaddition reaction as the method for synthesis of polymers.

1. CARBOSILOXANE COPOLYMERS WITH MONOCYCLIC FRAGMENTS IN THE CHAIN For the purpose of synthesizing poly(carbosiloxane) with cyclic tetrasiloxane fragments in the methyl siloxane backbone, hydride polyaddition of divinylorganocyclosiloxane by dihydrodimethylsiloxane was studied [10]. Polymers were synthesized in argon at 1:1 molar ratio of the initial reagents in the absence of diluter or in inert organic solvent (toluene) at 100 - 110°C. The reaction temperature was selected at the level causing no scission of organosiloxane rings. Platinum hydrochloric acid, double added to the reaction mixture in amount 1÷1.5×10-5 g of H2PtCl6x6H2O per 1 g of the initial mixture, was used as the catalyst. A half of this amount was added before the reaction initiation, and the second half 25÷140 hours after beginning of heating. Platinum hydrochloric acid was added in the form of 0.01 M solution in tetrahydrofuran. Isopropyl alcohol, used as diluter for H2PtCl6x6H2O, decreased relative viscosity of synthesized polymers, apparently, due to proceeding of side alkoxylation reaction: ≡Si-H+HO-C3H7 → ≡Si-O-C3H7 +H2 Linear poly(organocarbosiloxanes) with cyclic structures in the backbone were synthesized in ac-cordance with the following scheme [10]:

x [Me2SiO]2[MeVinSiO]2 +x H(SiMe2O)n-1SiMe2H

H2PtCI6

Me2 Si Me Me O O CH2-CH2 Si Si-CH2CH2-(SiMe2O)n-1SiMe2 O O Si Me2 I

x

Scheme 1

where n = 0, 1, 4, 5, 6, 10, 20, 27, 34, 57, 94, 150, 200. Synthesized polymers represent viscous and highly viscous colorless transparent liquids, soluble in cyclic hydrocarbons and lower eaters. The effect of reaction proceeding in an inert organic solvent (for example, toluene) on inherent viscosity of derived polymer is negligible. Obtaining of high viscosity values in the presence of solvent requires just longer-term heating up of the reaction mixture. To the authors’ point of view, polymers of such structure,

Organosilicon Copolymers with Carbocyclosyloxane Fragments…

151

possessing cyclic fragments in the backbone, are of interest due to their high reactivity. For example, these polymers are capable of easy formation of cross-linked structures in anionic catalysts. Initial divinylhexamethylcyclotetrasiloxane was synthesized by combined hydrolysis of dimethyldichlorosilane and methylvinyldichlorosilane. Despite the appli-cation of efficient rectification columns and analytical chromatograph with preparative add-on device, the attempts of the authors to separate isomeric 1,3- and 1,5divinylhexamethylcyclotetrasiloxanes, which may be formed in cooperative hydrolysis, have failed. That is why isomeric structural groups as follows (XIII) may also be present in synthesized polymers:

Me CH2-CH2 Si

Me O

O Me2Si

Si-CH2-CH2-(SiMe2O)n-1SiMe2 O

O

SiMe2 II

x

Semi quantitative assessment of the ratio of isomeric 1,3- and 1,5-cyclic structures in synthesized polymers with the help of NMR spectra was performed, which was found 1:1. In a series of processes variation of functional groups’ content (≡Si-H due to IRspectroscopy data) during reaction proceeding and type of the increase of reaction mixture specific viscosity were studied. Maximal viscosities of polymers ([η] = 0.17 - 0.97 dl/g) are reached after 50 – 160 hours of heating and in majority of cases depend on the length of α,ω−dihydropolydimethylsiloxane chain and purity of initial compounds used. Studies of IR spectra of synthesized poly(organocyclocarbosiloxanes) and preliminary experiments on long-term heating of the mixture of initial hexamethyldivinylcyclotetrasiloxane isomers under polyaddition conditions allow a suggestion that polymers are synthesized due to hydride polyaddition proceeding with preservation of structures of initial compounds, but not polymerization of cyclic hexamethyldivinylcyclotetrasiloxane. The presence of organocyclotetrasiloxanes fragments in the structure of synthesized poly(organocyclocarbosiloxanes) may be proved by their transition into non-fusible, insoluble state due to polymerization of organosiloxane cycles existing in the polymer structure. As reprecipitated polymers are heated at 100-110°C in the presence of 0.001–0.01 wt % of anionic polymerization catalysts, viscosity is considerably increased and gel is formed. Varying length of alkylenesiloxane bridge between organocyclotetrasiloxanes fragments of poly(organocyclocarbosiloxanes) backbone, one may change the average distance between cross-link points and, consequently, properties of cross-linked polymers formed. Hydride polyaddition between 1,5-divinyl-1,5-dimethyl-3,3,7,7-tetraorganocyclotetrasiloxane and me-thylphenylsilane has been studied [11]. All attempts to separate initial divinylorganocyclotetrasi-loxanes into cis- and trans-isomers have failed. Thus, according to NMR data, initial divinylorgano-cyclotetrasiloxanes represent a mixture of cisand trans-isomers. The reaction proceeds as follows:

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O. Mukbaniani, G. Zaikov, N. Mukbaniani et al. R' R" Me

CH2=CH2

x CH2=CH

Me

Me

+ x H Si H Ph

H2PtCI6 0

TC

Me

R' R"

CH2

R' R"

Me CH2-CH2 Si CH2 Ph Me

R' R"

x

I Scheme 2

Where: R′ = R′′ = Me = Ph; R′ ≠ R′′. Polyaddition was carried out at 60 – 70°C, and at the final stage the mixture was heated up to 100°C. The catalyst in amount 5×10-4 mol Pt/mol was added to vinylcyclosiloxane, heated up to 50°C. Some parameters of synthesized copolymers are shown in Table 1. For the purpose of synthesizing carbosiloxane copolymers with organocyclopentasiloxane fragments in the dimethylsiloxane backbone, hydride polyaddition of α,ωdihydridedimethylsiloxanes to l,5-ivinyl-l,5-dimethylhexaphenylcyclopentasiloxane in the presence of platinum hydrochloric acid as a catalyst was studied at temperatures below 100°C: at 75°C, 80°C and 85°C. Forasmuch as the initial 1,5-divinyl-1,5dimethylhexaphenylcyclopentasiloxane represents a mixture of cis- and trans-isomers (at the ratio copolymers derived from them are atactic. Preliminary heating of initial compounds within the temperature range of 80 - 95°C in the presence of the catalyst indicated that under these conditions organocyclopentasiloxane fragments are not polymerized. Table 1. Physical and chemical parameters of poly(organocarbosiloxane) copolymers of cyclolinear structure

No

1 2 3

Copolymer

Me CH2

R' R"

R' R" *

Me CH2-CH2 Si CH2 Ph Me

R′

R′′

[ η], dl/g

Me Me Ph

Me Ph Ph

0.08 0.06 0.04

Tdegr* of 5% mass Loss

Coke residue, (800°С), %

240 320 370

52 45 41

Тg, °С

-7 26 13

x

TGA data on polymers processed by heptamethylvinylcyclotetrasiloxane.

Copolymer structure was determined from 29Si NMR spectral data. The reaction proceeding was detected by a decrease of amount of active ≡Si-H groups. It was observed that the rate and depth of pol-yaddition decrease with the increase of α,ωdihydridedimethylsiloxanes chain length. Hydride polyaddition proceeds in accordance with the following scheme 2 [12,13]:

Organosilicon Copolymers with Carbocyclosyloxane Fragments…

Ph2

Vin x Me

153

Me H PtCI + xH(SiMe2O)n-1SiMe2H 2 0 6 TC Vin

Ph2 Ph2 Ph2 Me CH2-CH2 (SiMe2O)n-1SiMe2CH2

CH2 Me

Ph2 Ph2

x

III

Scheme 3

Where: n = 2 ÷23. Table 2. Physical and chemical parameters of structure III carbosiloxane copolymers containing cyclopentasiloxane fragments

№

Copolymer

nSiO

1 2 3 3′ 3′′

CH2

Ph2 Me

Me Me C2H4 (SiO)n-1SiCH2 Me Me

Me Ph2 Ph2

4 5 *

x

Yield, %

Reactio n T,0C

η*sp

Tg, 0 C

d1 , Å

5% mass losses

Μω x10-3

2

75

85

0.09

0÷-2

9.20

320

189

4

80

85

0.14

-22

-

-

-

6

92

75

0.15

-

-

-

-

6

93

80

0.18

-

-

-

-

6

95

85

0.20

-53

-

295

211

12

95

85

0.24

-82

-

-

-

23

96

85

0.31

-123

7.21

285

236

0

In toluene at 25 C

As a result of the reaction, copolymers with ηspec = 0.09 – 0.26 are obtained, which are liquid or glassy light-yellow products, soluble in ordinary organic solvents. Some physical and chemical parameters and the yield of copolymers are listed in Table 2. As indicated by the data in the Table, in the case of short lengths of the dimethylsiloxane backbone, n, the yield of copolymers is low. This may be explained by the fact that besides intermolecular reaction, intramolecular cyclization proceeds forming a polycyclic structure. This conclusion is in agreement with data from the literature [13 - 18]. The amount of active ≡Si-H groups was decreased during proceeding of hydride polyaddition. Figure 1 shows that the rate of hydride polyaddition increases with temperature (at one and the same values of dimethylsiloxane units, n), but on the other hand, with an increase of the length of dimethylsiloxane links (n) at the same temperatures, the rate of hydride polyaddition decreases. Figure 1 shows that conversion of active ≡Si-H groups is not complete and decreases from 20% (n = 6) to 15% (n = 12).

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Figure 1. Time dependence of changes in active ≡Si-H% groups during polyaddition of α, ω−dihydridedimethylsiloxane (n = 6) with 1,5-divinyl-1,5-dimethylhexaphenylcyclo-pentasiloxane: 1 - at 85°C; 2 - at 80°C and 3 - at 75°C.

It was found that polyaddition is the second order reaction. The reaction rate constants and the activati-on energy were calculated: k75oC=1.4004×10-2, k80oC=1.965×10-2, k85oC=2.559×10-2 l/mol⋅s; Eact=62.1 kJ/mol, respectively. 1 H NMR spectra of copolymers indicate that catalytic hydride polyaddition mainly proceeds by the Farmer rule with formation of dimethylenic bridges. In these spectra a reflex of –СН2-СН2- group with chemical shift δ=0.34 ppm is observed; it is indicated that hydride polyaddition partly (about 6-7%) proceed by the Markovnikov rule. Cyclolinear carbosiloxane copolymers with 1,7- and 1,5-disposition of dimethyloctaphenylcyclohexa-siloxane fragments in the dimethylsiloxane backbone were synthesized by hydride polyaddition of α,ω-dihydridedimethylsiloxane to 1,7-divinyl-1,7dimethyloctaphenylcyclohexasiloxane and 1,5-divinyl-1,5-dimethyloctaphenylcyclohexasiloxane in the presence of a catalyst. Polyaddition reactions were studied below 100°C. It was also indicated that under these conditions polymerization or polycondensation of initial compounds does not take place. Polyaddition proceeds in accordance with the following scheme 3 [19-21]:

Me x Vin

Me

O(SiPh 2 O) l Si

Si

+ xH (SiM e 2 O) n-1 SiMe 2 H

O (SiPh 2 O) m Vin Me CH2 Si

Me

O(SiPh2O)l

Si C2H4 O(SiPh2O)m IV, V

Scheme 4

H 2 PtCI 6 0

T C

Me Me (SiO)n-1SiCH2 Me Me

x

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Where: m = l = 2 (IV); n = 2 ÷ 23; l = 1, m = 3 (V); n = 2 - 23. Forasmuch as 1,7- and 1,5-divinylcyclohexasiloxanes, used in polyaddition, represent mixtures of cis- and trans-isomers of the approximate 52:48 ratio, synthesized copolymers are atactic. Reprecipitation of copolymers from toluene solution by methyl alcohol has given viscous or solid (with regard to the value of flexible junction) transparent products with ηspec=0.09-0.29, well soluble in different organic solvents. It is found that at short length of dimethylsiloxane unit (n ≤ 4), copolymer yields are slightly decreased that may be explained by partial proceeding of hydride polyaddition by intramolecular cyclization mechanism (see Tables 3 and 4). Table 3. Physical and chemical parameters of carbosiloxane copolymers with 1,7disposition of cyclic hexasiloxane fragments in the dimethylsiloxane backbone (structure IV) №

Copolymer

1 2 3 3′ 3′′ 4 5 *

Me

Ph 2 Ph 2

Me

Ph 2 Ph 2

Me Me C 2H 2 (SiO)n-1SiCH 2 Me Me x

nSiO

Yield, %

Reaction T,0C

η*sp

Tg, 0 C

d 1, Å

2 4 6 6 6 12 23

74 80 94 94 95 96 95

90 90 80 80 85 90 90

0.10 0.12 0.17 0.17 0.18 0.23 0.29

+5 -10 -40 -68 -123

9.31 8.81 8.40 7.24

5% mass losses 280 280 260

Μωx1 0-3 174 194 231

In toluene at 25°C.

After solvent removal from the mother solution of re-precipitated copolymer 1 (Table 2), a semicry-stalline compound with the molecular mass equal ~1100 was obtained [20, 21]. The product of intra-molecular cyclization of 1,7-divinyl-1,7dimethyloctaphenylcyclohexasiloxane and 1,3-dihydride-tetra-methyldisiloxane of the following structure only may display the current molecular mass: because divinylorganocyclohexasiloxane of the trans-structure participates in formation of macromolecular chain. Table 4. Physical and chemical parameters of carbosiloxane copolymers with 1,5– position of cyclic hexasiloxane fragments in the dimethylsiloxane backbone (structure V) № 1 2 3 3′ 3′′ 4 5 *

Copolymer

Ph2 Me Me Me C2H2 (SiO)n-1SiCH2 Me Me Ph2 Ph2 Ph2 x

Me

In toluene at 25°C.

Tg, 0 C

d 1, Å

0.09

+8

9.60

5% mass losses 270

0.11

-12

-

-

-

0.15 0.18 0.15 0.22 0.28

-38 -72 -123

8.90 8.34 -

265 260

180 210 -

nSiO

Yield, %

Reaction T,0C

η*sp

2

72

10

4

84

85

6 6 6 12 23

86 89 94 95 95

80 90 100 100 100

Μωx1 0-3 159

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Structure and composition of synthesized cyclolinear carbosiloxane copolymers were determined by functional and ultimate analysis, IR and NMR spectral data. Some parameters of copolymers are shown in Tables 3 and 4. A reflex with chemical shift at δ = 0.35 ppm typical of –СН2-СН2-group is observed in 1 Н NMR spectrum of copolymer 1 (Table 3). This indicates that polyaddition proceeds pursuant to the Farmer rule. A duplet centered at δ=1.06 ppm, corresponded to methyl protons in =СН-СН3 group, is also observed in the spectrum. Based on the ratio of intensities, it was concluded [20, 21] that polyaddition partly proceeds by the Markovnikov mechanism (6 –8%). A complex multiplet with chemical shift at δ=5.6 - 6.2 ppm typical of vinyl protons not entered polyaddition reaction, and a singlet for ≡Si-H protons with chemical shift at δ = 4.4 ppm, not participated in the reaction, too, were observed in the spectra. Hydride polyaddition proceeded at different temperatures. Figures 2 and 3 show variations of ≡Si-H bond concentration during polyaddition of α, ω−dihydridedimethylsiloxane (n = 6) to 1,7-divinyl-1,7-dimethyloctaphenylcyclohexasiloxane and 1,5-divinyl-1,5-dimethyloctaphenylcyclohexasiloxane. It is observed that hydride polyaddition depth is increased with the reaction temperature. Moreover, the effect of 1,7- or 1,5-disposition of vinyl groups in cyclohexasiloxane fragments is the negligible factor for their reactivity. It is found that at the initial stages, polyaddition represents the second order reaction. In the case of 1,7-divinyl-1,7-dimethyloctaphenylcyclohexasiloxane, polyaddition rate constants for different tempera-tures were determined as follows: k90oC = 3.0797×10-2; k85oC =2.3007×10-2; k80oC = 1.6781×10-2 l/mol⋅s. Activation energies for 1,7-divinyl-1,7dimethyloctaphenylcyclohexasiloxane and 1,5-divinyl-1,5-dimethyl-octaphenylcyclohexasiloxane were also calculated: Еact= 66.7 and Eact =69.7 kJ/mol, respectively. Obviously, these values are very close.

Figure 2. Decrease of ≡Si-H bond concentration during hydride polyaddition of α, ω−dihydridedimethylsiloxane (n = 6) to 1,7-divinyl-1,7-dimethyloctaphe-nylcyclohexasiloxane: 1 - 90°C; 2 85°C; 3 - 80°C.

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Figure 3. Decrease of ≡Si-H bond concentration during hydride polyaddition of α, ω−dihydridedimethylsiloxane (n = 6) to 1,5-divinyl-1,5-dimethyloctaphenyl-cyclohexasiloxane: 1 - 100°C; 2 - 90°C; 3 - 80°C

X-ray diffraction studies have indicated that copolymers are single-phase amorphous systems, and maximal interchain distance is observed for short dimethylsiloxane unit length (n = 2); hence, for copolymer 1 (Table 4), d1 = 9.60 Å. This value is slightly greater than the interchain distance of carbosiloxane copolymer 1 (Table 3) with 1,7-disposition of cyclohexasiloxane fragment in the dimethylsiloxane backbone (n = 2). As flexible junction length is increased, d1 decreases and approaches the interchain distance in PDMS; it increases with the volume of cyclic fragment at the same lengths of flexible dimethylsiloxane unit, i.e. at transition from cyclopentasiloxane to cyclohexasiloxane fragment. Thermogravimetric studies of carbosiloxane copolymers have indicated 5% mass loss of the compounds in the temperature range of 250 - 260°C. The main degradation process proceeds in the range of 380 - 630°C, and above 700°C the mass loss is not observed. It is found that thermal oxidative stability of copolymers is decreased with increase of the cyclic fragment volume, i.e. at the transition from cyclic pentasiloxane to hexasiloxane fragments in cyclolinear carbosiloxane copolymer. It is also found that carbosiloxane copolymers with 1,7and 1,5-disposition of cyclic hexasiloxane fragments in the backbone are characterized by almost identical thermal oxidative stability. Thus, it was concluded [20, 21] that the effect of 1,7- or 1,5-disposition of cyclic hexasiloxane fragment in carbosiloxane copolymer is negligible for thermal oxidative stability of copolymers (Figure 4). On the other hand, compared with pure siloxane analogues, thermal oxidative stability of carbosiloxa-ne copolymers is lower. Thermogravimetric studies have displayed that the cyclic fragment causes a considerable effect on carbosiloxane copolymer at n=12 only, and at n=23 no effect of cyclic fragment on the glass transition temperature of the copolymer is observed. Figure 5 shows dependence of Tg on the length of dimethylsiloxane unit for cyclolinear carbosiloxane copolymers.

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Figure 4. Thermogravimetric curves of carbosiloxane copolymers: 1 – copolymer 4 (Table 4) with 1,5disposition of cyclic hexasiloxane fragment in the backbone; 2 –co-polymer 1 (Table 3) with 1,7-disposition of cyclic hexasiloxane fragment in the back-bone; 3 – copolymer 1 (Table 2) with cyclic pentasiloxane fragment in the backbone.

Figure 5. Dependence of Tg for cyclolinear carbosiloxane copolymers on the length of dimethylsiloxane unit: 1 – copolymer with 1,7-position of cyclic hexasiloxane fragment; 2 – copolymer with 1,5-position of cyclic hexasiloxane fragment.

It has been found that expansion of the cyclic fragment volume at the same length of dimethylsiloxane unit, i.e. introduction of a single diphenylsiloxane unit, Tg of the copolymer is increased by ~10°C. It is also shown that the effect of 1,7- or 1,5-disposition of cyclic hexasiloxane fragment on Tg of the copolymer is negligible, which conform to the previous results on pure siloxane copolymers [22].

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2. CARBOSILOXANE COPOLYMERS WITH TRICYCLIC FRAGMENTS IN THE BACKBONE The present Chapter discusses synthesis and studies of carbosiloxane copolymers containing flexible dimethylsiloxane and decaorganotricyclodecasiloxane fragments in the backbone [23, 24]. For the purpose of synthesizing carbosiloxane copolymers, hydride addition of α,ω-dihydridedimethylsiloxane to 1,3-divinyl-1,3,9,9,11,11-hexamethyl5,7,13,15-tetraphenyltricyclodecasiloxane was performed at temperature below 90°C. Therefore, cyclosiloxane ring disclosure did not take place under conditions of hydride polyaddition. Preliminary heating of initial divinylorganotricyclodecasiloxane during 10 hours by temperature of 70 - 90°C in the presence of rhodium acetylacetonatedicarbonyl or platinum hydrochloric acid as a catalyst did not initiate polymerization of the primary divinyltricyclodecasiloxane. Thorough analysis of the reaction mixture by gas liquid chromatography method has detected the presence of initial organosiloxanes. Besides, there are no changes in the NMR and IR spectra of divinyl-containing compounds and dihydridedimethylsiloxanes. Hydride polyaddition of divinyl-containing compounds was carried out for various lengths of α,ω-dihydridedimethylsiloxanes. The reaction run was searched by a decrease of active ≡Si-H groups’ concentration. It was found that for rhodium acetylacetonatedicarbonyl as a catalyst, copolymers soluble in organic solvents were obtained, which were structured after some time. This may be explained by the fact that in spite of polymers re-precipitated from toluene solution by methyl alcohol, rhodium catalyst remains in polymeric systems, which decompose and induce structuring (cross-linking) of copolymers. Therefore, copolymers were synthesized in the presence of platinum hydrochloric acid as the catalyst. The rate and depth of polyaddition are decreased with the increase of α,ωdihydride-dimethylsiloxane chain length. Figure 6 shows that conversion of ≡Si-H bond is incompletely and decreases from 95% (n = 4) to 83% (n = 12). Hydride polyaddition of α,ω-dihydridedimethylsiloxane to divinylorganotricyclodecasiloxane proceeds in accordance with the general scheme as follows [23, 24]: R m Vin

R Vin + mH(SiMe2O)n-1SiMe2H

Cat

R

R

C2H4

C2H4-(SiMe2O)n-1 SiMe2

Ph

Ph

Ph

Ph

Ph

Ph

Ph

Ph

Me2

Me2

Me2

Me2 VI

Scheme 5 Where: n = 2 ÷21; Cat is H2PtCl6.

m

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Figure 6. Time dependence of ≡Si-H group concentration (%) for polyaddi- tion of α,ωdihydridedimethylsiloxane to divinylorganotricyclodecasiloxane at 90°C for dimethylsiloxane backbone lengths: 1) n = 12; 2) n = 6; 3) n = 4

As a result of the reaction, synthesized copolymers possess ηspec = 0.08 -0.26 and represent liquid or glassy-like light yellow transparent products, soluble in ordinary organic solvents. Some physical and chemical parameters, molecular weights and yields of synthesized copolymers are shown in Table 6. Table 6. Some physical and chemical parameters of carbosiloxane cyclolinear copolymers with tricyclodecasiloxane fragments in the backbone №

1 2 3 4 5 6 7 *

Copolymer structure

R C2H4

nSiO

R C2H4(SiMe2O)n-1SiMe2

Ph

Ph

Ph

Ph

Me2

Me2

m

2 4 4 4 6 12 21

Yield, % 80 83 88 91 92 93 94

Treact, 0 C 90 70 80 90 90 90 90

η*sp

Tg, 0C

d1,Å

Μω*10-3

0.08 0.09 0.11 0.11 0.14 0.20 0.26

-12 -50 -96 -123 -123

10.20 8.68 7.54

72 85 110

In toluene at 25°C; molecular masses were determined by the gel chromatography method.

The reaction proceeding was also monitored by viscosity increase of synthesized copolymers. It was found that viscosity of copolymers and the hydride polyaddition degree increase with temperature rise to 70 - 90°C. In hydride polyaddition of α,ωdihydridedimethylsiloxane to divinylorganotricyclodecasiloxane, conversion of ≡Si-H bond increases with temperature as follows: from 85% (70°C) to 95% (90°C). Figure 7 shows time dependence of ≡Si-H concentration (%) decrease for various temperatures. Time dependence of reverse reagent concentration displays the second order of hydride polyaddition. Further on, reaction rate constants for various temperatures were calculated:

Organosilicon Copolymers with Carbocyclosyloxane Fragments…

161

k700C≈1.1086x10-2, k800C≈ 1.6196x 10-2, k900C≈2.3834x10-2 l/mol⋅s. It was shown that the reaction rate constants increase by 1.5 times, approximately, for every 10°C of temperature rise. Activation energy of hydride polyaddition was derived from dependence of the reaction rate constant logarithm on reverse temperature: Eact=64.4 kJ/mol.

Figure 7. Time dependence of ≡Si-H group concentration (%) in polyaddition of α,ωdihydridedimethylsiloxane (n = 4) to divinylorganotricyclodecasiloxane: 1 - 90°C; 2 - 80°C; 3 - 70°C

Study of 1H NMR spectrum for copolymer 2 (Table 6) displays that catalytic hydride polyaddition mainly proceeds by the Farmer rule with formation of dimethylene bridges. NMR spectrum also displays a reflex of -CH2-CH2- group with chemical shift of δ=0.35 ppm. A duplet reflex centered at the chemical shift of δ=1.12 ppm, corresponded to methyl protons in =CH-СН3 groups with 5–6% concentration was also observed. Integral ratios of methyl and phenyl protons correspond to the formula of copolymer 2(Table 6).

Figure 8. Tg dependence of cyclolinear carbosiloxane copolymers (VI) on length of linear poly(dimethylsiloxane), n.

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Thermomechanical studies of synthesized copolymers indicate that the glass transition temperature of copolymers is decreased with an increase linear dimethylsiloxane backbone length, n (Figure 8). Since n=12 carbotricyclodecasiloxane fragments in copolymers cause no effect on the dimethylsiloxane backbone and Tg of copolymer 6 (Table 6) remains equal 123°C. Contrary to previous considerations [25], dimethylsiloxane backbone length increase (n=21) does not cause formation of two-phase systems in cyclolinear copolymers with rigid decaphenyltricyclodecasiloxane fragments and flexible dimethylsiloxane units (n = 25). Comparison of copolymers containing carbotricyclodecasiloxane and tricyclodecasiloxane fragments [[25] displayed lower glass transition temperatures of the former, which may be explained by excessive concentration of flexible -CH2-СН2- groups in its backbone.

Figure 9. Thermogravimetric curves of cyclolinear carbosiloxane copolymers: 1 - copolymer 7; 2 copolymer 5; 3 - copolymer 1(Table 6, in air, at 5 deg/min heating rate)

Thermogravimetric studies of copolymers show (Figure 9) their higher thermal oxidative stability for short length of the dimethylsiloxane backbone, n. As the length of dimethylsiloxane backbone increases, thermal oxidative stability of copolymers decreases. Compared with siloxane analogies, thermal oxidative stability of carbotricyclodecasiloxanecontaining copolymers is lower [25]. In the temperature range of 300 - 350°C mass losses of the polymer are below 3 - 7%, and the main degradation process proceeds at 400-650°C. Above 650°C, the curves of mass losses are preserved unchanged (Figure 9). As carbotricyclodecasiloxane fragments are introduced into the dimethylsiloxane backbone, the main degradation process proceeds at temperature by 80 - 100°C higher than for unblocked poly(dimethyl-siloxane).

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Synthesized copolymers were studied by the X-ray diffraction method. Diffraction patterns of amorphous polymers (Figure 9) show that the interchain distance reaches its maximum (d1=10.24 Å) at short lengths of flexible dimethylsiloxane backbone, n. As the length of dimethylsiloxane backbone increases (n = 21), the interchain distance decreases and for copolymer 5 reaches 7.54 Å (Table 6).

Figure 10. Diffraction patterns of copolymers: 1 - copolymer 5; 2 – copolymer 1 (Table 6).

Thus copolymer 7 does not form a two-phase system, as observed for copolymers with decaphenyltricyclodecasiloxane fragments in the dimethylsiloxane backbone. This may be explained by the presence of combination of rigid carbotricyclosiloxane and flexible dimethylsiloxane fragments in it. Therefore, copolymers represent single-phase systems. For the purpose of synthesizing carbosiloxane copolymers with tricyclohexasiloxane fragments in the backbone, hydride polyaddition of α,ω-dihydridepoly(dimethylsiloxanes) to 1,7-divinyl-1,7-dimethyl-3,5,9,11-tetraphenyltricyclohexasiloxane was studied [26]. The reaction was implemented in anhydrous toluene in the presence of platinum-hydrochloric acid in tetrahydrofuran and in the temperature range of 70 – 170°C according to the following scheme:

Ph x

Ph

O

R Si Vin

Me Me Me + x H-Si-O-(Si-O)-Si-H Si n Vin Me Me Me O R

O

O Ph

H2PtCI6

Ph

R

Ph O

Ph O

C2H4 Si

R Si C2H4 (SiMe2O)n+2

O Ph

O Ph VII

Where: R = Me, Ph; n = 0 ÷ 86.

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New cyclolinear carbosiloxane copolymers containing organotricyclohexasiloxane fragments in backbones were synthesized in the reaction. They represent viscous liquids with molecular mass varying in the range of 35x103 - 45 x103. The influence of organotricyclohexasiloxane fragments in carbosiloxane copolymer on thermal oxidative degradation proceeding was studied. It is found that the increase of concentration of rigid organo-tricyclohexasiloxane fragments in linear chains of polymers rise their resistance to thermal oxidative degradation. For example, 15% mass loss of structure VII copolymers (R =Ph, n = 74 and R = Me, n = 86) is observed at 380 and 420°C, respectively. For copolymer with n = 0, it is observed at 540°C. Thus, the increase of cyclic fragments’ concentration in the linear chain induces rise of macromolecular chain rigidity and leads to formation of a one-phase system. The increase of cyclic fragments’ concentration in the macromolecular chain raises thermal oxidative stability of the copolymers.

REFERENCES [1] [2] [3] [4] [5] [6] [7] [8]

[9] [10] [11] [12]

[13]

Pomerenceva M.G., Beliakova Z.V., Golubtsova S.A. In the book “obtaining carbofunctional organosilanes by addition reaction”. M., NIITEkhim., 1971. (Rus) Reikhsfeld V.O., Vinogradova V.N., Fillipova N.A. Zhurn. Obshch. Khim., 1973, v.43, №10, p. 2216. (Rus) Fillipova N.A., Reikhsfeld V.O., Zaslavskaia T.N., Kuzmina T.A. Zhurn. Obshch. Khim., 1977, v. 47, №6, p.1374. (Rus) Andrianov K.A., Magomedov G.K. Dokl. AN USSR, 1973, v. 228, No5, p. 1094. (Rus) Watanabe H,m Kitahara T., Motegi X., Nagai H. Journ. Organometallic Chem., 1977, v.139, No2, p.215. (Rus) Mileshkevich V.P., Kauchuk i Resina, 1978, № 6, p. 4. (Rus) Andrianov K.A., Souchek I., Khananashvili L.M. Uspekhi Khimii, 1979, v. 48(7), p.1233. Mukbaniani O.V., Zaikov G.E. New Concepts in Polymer Sciences, Cyclolinear Organosilicon Copolymers: Synthesis, Properties, Application, VSP, Utrecht-Boston, 2003, p. 499. Severni V.V., Flaks E.Yu., Zhdanov A.A., Vlasova V.A., Andrianov K.A., Vishnevski F.N. Vysokomol. Soedin., 1974, v.16(A) (2), p. 419. (Rus) Zhdanov A.A., Andrianov K.A., and Malyikhin A.P., Doklady AN SSSR,1973, v. 211(5), p. 104. (Rus) Zhdanov A.A., Pryakhina T.A., Strelkova T.V., Afonina R.I., and Kotov V.M., Vysokomol. Soed., 1993, v. 35(5), p. 475. (Rus) Karchkhadze M.G., Mukbaniani N.O., Samsonia A.Sh., Tkeshelashvili R.Sh., Kvelashvili N.G., Chogovadze T.V., and Khananashvili L.M., Bull.Georg. Acad. Sci., 1998, v. 158(1), p. 75. Mukbaniani O.V., Organosiloxane Copolymers and Block-copolymers With Different Cyclic Structure of Macromolecules, Doctor’s Dissertation on Chemistry, 1993, Tbilisi State University, Tbilisi, Georgia. (Rus)

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[14] Koiava N.A., Mukbaniani O.V., and Khanashvili L.M., Vysokomol. Soedin.,1985, v. 27A, №11, p. 2261. (Rus) [15] Koiava N.A., Mukbaniani O.V., and Khananashvili L.M., Abstr. Commun.27th Intern. Symp. Macromol., Strasburg, 1981, p. 18. [16] Mukbaniani O.V., Meladze S.M., and Khananashvili L.M., Vysokomol.Soedin., 1984, v. 24B №4, p. 250. (Rus) [17] Andrianov K.A., Nogaideli A.I., Makarova N.N., and Mukbaniani O.V., Izv. AN USSR, Ser. Khim., 1977, №6, p. 1388. (Rus) [18] Zhdanov A.A. and Astapova T.V., Vysokomol. Soedin., 1981, v. 23A, №3, p. 626. (Rus) [19] Mukbaniani N.O., Synthesis and Investigation of Properties of Carbosiloxane Cyclolinear Copolymers, Candidate’s Dissertation on Chemistry, 2001, Tbilisi State University, Tbilisi, Georgia. [20] Karchkhadze M.G., Mukbaniani N.O., Khananashvili L.M., Meladze S.M., Kvelashvili N.G., and Doksopulo T.P., Intern. J. Polym. Mater., 1998, v.41, p. 89. [21] Mukbaniani N.O., Karchkhadze M.G., Samsonia A.Sh., Tkeshelashvili R.Sh., and Khananashvili L.M., Bull. Georg. Acad. Sci., 1999, v. 160, №1, p. 84. [22] Andrianov К.А., Tsvetkov V.N., Tsvankin D.Y., Nogaideli A.I., Makarova N.N., Vitovskaia M.G., Genin Y.V., Kolbina G.F., Mukbaniani O.V. Vysokomol. Soed., 1976, v.18А, № 4, p.890. [23] Mukbaniani O.V., Khananashvili L.M., Karchkhadze M.G., Tkeshelashvili R.Sh., and Mukbaniani N.O. In: Synthesis and Properties of Polymers, Nova Science Publishers, Inc., Commack., 1996, p.89. [24] Mukbaniani O.V., Khananashvili L.M., Karchkhadze M.G., Tkeshelashvili R.Sh., and Mukbaniani N.O. Intern. J.Polym. Mater., 1996, v.33, p.47. [25] Inaridze I.A., Synthesis and Investigations of Polyorganosiloxanes with organocyclosiloxane and orgacarbocyclosiloxane Fragments in the Chain, Candidate’s Dissertation on chemistry, Tbilisi State University, 1993, Tbilisi, Georgia. [26] Klementiev I.Yu., Investigations in the Field of Synthesis and Transformation of Polycycloorganosiloxanes, Candidate’s Dissertation on chemistry, M.V. Lomonosov Institute of Fine Chemical Technology, 1979, Moscow, USSR. (Rus).

In: Chemical and Biochemical Physics: New Frontiers ISBN 1-60021-165-8 Editor: G. E. Zaikov, pp. 167-216 © 2006 Nova Science Publishers, Inc.

Chapter 15

ORGANOSILICON OLIGOMERS AND COPOLYMERS OF BEAD-SHAPED STRUCTURE O. Mukbaniani1, G. Zaikov2 and T.Tatrishvili1 1

2

I. Javakhishvili Tbilisi State University, Tbilisi, Georgia Institute of Biochemical Physics, Russian Academy of Sciences, Moscow, Russia

INTRODUCTION The present state of the synthesis of silicon organic oligomers and polymers of beadshaped struc-ture is reviewed by condensation techniques, but not by polymerization or exchange polymerization, because in the latter cases, primary siloxane procurements may not be preserved due to instability of ≡Si-О-Si≡ bond in cyclosiloxanes. Equilibrium rigidity of cyclolinear polyorganosiloxanes, macromolecules of which are composed of different sized rings linked by oxygen atoms or other flexible bond bridges, depends upon the number of flexible units both in the ring and linear chain. A broad selection of cyclic structures in the chain (“beads in the necklace”), regulation of their size and type of bonding allow significant variations in properties of cyclolinear poly(organosiloxanes). Recently, contribution of dimethylsiloxane unit in the series of cyclic (D3 - D8) and linear (D2 - D11) oligodimethylsiloxanes with various end groups was studied [1–4]. It is indicated that absolute values of the activation energy of viscous flow of each cyclic compound are higher, compared with linear ones possessing the same number of dimethylsiloxane units in the molecule. Later on, Andrianov et al. have studied contribution of cyclic groups in polydimethylsiloxane up to direct bonding of organocyclosiloxanes to one another [5]. Comparison of properties of compounds which are structural isomers have indicated that in the absence of dimethylsiloxane bridges eva-poration temperatures and activation energies of viscous flow of bicyclic ones are higher than for their structural isomers possessing dimethylsiloxane units between cycles. The values of the activa-tion energy obtained for bicyclic compounds with dimethylsiloxane bridges of different lengths indicate that higher cohesive energy and, consequently, stronger intermolecular interactions are ty-pical of bis(organocyclosiloxy)oxides.

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1. BEAD-SHAPED ORGANOSILOXANE OLIGOMERS AND COPOLYMERS WITH ORGANOCYCLOTETRA(PENTA, HEXA)SILOXANE FRAGMENTS IN THE BACKBONE The present section discusses investigation results of the basic regularities and mechanisms of dihydroxyorganocyclosiloxanes interaction with dihydroxy(dichloro, dihydride)organocyclosiloxa-nes, clears up synthetic abilities of homo- and heterofunctional condensation in the field of syn-thesizing cyclolinear oligomers, and considers surveys of thermal and other physical and chemical properties of synthesized oligomers. Described in the literature is the method for obtaining cyclolinear oligomers by homocondensation of 1,3-dihydroxytetraphenylcyclotrisiloxane in the toluene solution [6]. Deep-level proceeding of condensation reaction is detected by elimination of ≡Si-H absorption band in IR-spectra. For obtain-ing organosiloxane oligomers of the bead-shaped structure, homocondensation of 1,3-dichlorotetra-organocyclotrisiloxane in the presence of sodium hydroxide in xylene solution has also been studied [6, 7]. The reaction proceeds in accordance with the scheme as follows: Ph

O

m CI-Si

Ph Si-CI

O

2m NaOH

Ph HO

O

Si

Si-O

H

-2mNaCI

O

O

R'

R

O Si

Si R

Ph

R'

m

I

Scheme 1

Where: R=Ph, p-C6H4CH3; m≈3÷50. Indicated in the present work is that the reaction results in formation of difficultly soluble com-pounds, which apparently shows that the effect of sodium hydroxide on 1,3dichlorotetraphenyl- cyclotrisiloxane induces disclosure of organocyclotrisiloxane unit, because the catalyst used may not only induce homocondensation, but also acts as the anionic catalyst of organocyclosiloxanes poly-merization. As a result, composite materials derived from these oligomers were suggested as elec-trical insulating materials. Homofunctional condensation of dihydroxyorganocyclosiloxanes was studied using catalysts of sila-nol condensation [8]. Despite high variety of catalysts accelerating silane condensation due to cata-lytic action, they may be divided into two groups, which are equilibrating and non-equilibrating ca-talysts [9 – 11]. To the first group the catalysts are corresponded, in the presence of which conden-sation proceeds with ≡Si-O-Si≡ bond cleavage, and the second group is composed of catalysts, which do not induce cleavage of the siloxane bond. Studying synthesis of organosiloxane oligomers, the authors of the present monograph have sur-veyed reactions of homofunctional condensation of 1,5dihydroxyorganocyclotetrasiloxanes [12, 13] 1,5-dihydroxyorganocyclopentasiloxanes [14] and 1,7-dihydroxyorganocyclohexasiloxanes [15] in different solvents in the presence of the catalyst (activated coal), and at boiling temperature of solvents used.

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169

Homofunctional polycondensation of studied dihydroxy-containing organocyclotetra(penta, hexa)-siloxanes proceeds in accordance with the schemes follows:

O(SiPh2O)k R R Càct, solvent m HO Si Si OH O(SiPh2O)l

O(SiPh2O)k

R HO

Si

R Si O H

O(SiPh2O)l

m

Scheme 2

Where: R=Me, Ph, l=k=1 (II), l=1, k=2 (III); l=k =2 (IV); m=4÷30. Synthesized copolymers of the bead-shaped structure are colored light yellow transparent products, well-soluble in organic solvents. Application of solvents with different boiling temperatures to this reaction causes variation of the polymerization degree (m). The level of homofunctional poly-condensation is increased with the boiling temperature of the solvent. The polycondensation level is also highly dependent on concentration of the catalyst applied to the reaction, which is activated coal. As the concentration of activated coal is increased from 7 to 15 wt.%, in the case of organo-cyclotetrasiloxane, the polymerization degree is increased, approximately, by 10 units. It should be noted that the increase of radical volume at silicon atom in organosilsesquioxane unit of organocyclosiloxanes induces a decrease of the polymerization degree (m) of oligomers. As the volume of cyclic fragments is increased, i.e. at transition from organocyclotetrasiloxane to organo-cyclopenta- and -hexasiloxane fragments, the depth of homofunctional condensation is decreased. To compare the depth of homo- and heterofunctional condensation of organocyclosiloxanes, cataly-tic dehydrocondensation of dihydroxyorganocyclotetra(penta, hexa)siloxanes with dihydride orga-nocyclotetra(penta, hexa)siloxanes was studied [16]. Recently, catalytic dehydrocondensation reacti-ons were successfully applied to synthesis of linear organosiloxane copolymers [17– 21]. The study of this reaction between tetramethylcyclotetrasiloxane and cis-1,3,5,7-tetrahydroxytetraphenylcy-clotetrasiloxane in the presence of potassium or sodium methoxide is considered [22]. It indicates that insoluble polymer content is increased with the hydrogen conversion. In spite of contradictory data on the application of platinum-hydrochloric acid in dehydrocondensation reaction, present in the literature [23, 24], besides platinum-hydrochloric acid, catalytic quantity of anhydrous powder-like caustic potash as the catalyst was used in catalytic dehydrocondensation reactions of dihydroxy-organocyclosiloxanes with dihydride organocyclosiloxanes [16], which are to synthesize organosilo-xane copolymers of the bead-shaped structure. Preliminary heating of initial organocyclosiloxanes during several hours at 40 - 50°C in the presence of anhydrous caustic potash (0.1 wt.% of total quantity of the initial components) and 0.1 M of platinum-hydrochloric acid solution in tetrahydro-furan (~5×10-4 g per 1 g of the substance) has indicated that no polymerization of initial cycles proceeds. Catalytic dehydrocondensation has been studied at different temperatures (20, 30 and 40°C) in the absolute toluene solution. It has been found that at initial stages of the reaction a short induction period (~1 – 2 min) is observed. Hydrogen conversion in the reaction with time has been studied. It has been found that in dehydrocondensation reaction, hydrogen conversion is

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increased from 66-80% (at 20°C) to 82-97% (at 40°C) with temperature (Catalyst H2PtCI6 and KOH accordingly). To increase the level of catalytic dehydrocondensation at the final stage of the reaction, the reaction products were heated up to 80°C during 3 – 4 hours. General scheme of dehydrocondensation proce-eding is as follows [16, 25]:

R

O(SiPh2O)n R

Me

Si OH + x H Si

x HO Si

O(SiPh2O)m Me Si H O(SiPh2O)m

O(SiPh2O)n

Cat -H2

R O(SiPh2O)n Me O(SiPh2O)m H O Si Si O Si Si H O(SiPh2O)n R O(SiPh2O)m Me x Scheme 3

Where: R = Me, Ph; m = n = 1, 2. Resulting the above-mentioned reaction, solid transparent copolymers, well soluble in usual organic solvents with ηspec = 0.06 – 0.13, are obtained after reprecipitation. Some properties of obtained co-polymers are shown in Table 1. Since initial dihydride- and dihydroxyorganosiloxanes, used in dehydrocondensation, represent a mixture of cis- and trans-isomers, synthesized copolymers possess atactic structure. As observed from the data, catalytic dehydrocondensation proceeds at a deeper level with formation of higher molecular products, than in the case of homofunctional products. It is shown [16, 25] that besides the origin and quantity of the catalyst, temperature and origin of the solvent, etc., reactivity of ≡Si-H bond is highly affected by steric and inductive factors, induced by cyclic structures and framing groups disposed at silicon atoms. Figure 1 show hydrogen conversions for dehydrocondensation at different temperatures of catalysts. It has been found that catalytic dehydrocondensation reaction displays the second order. Dehyd-rocondensation reaction rate constants are determined, and catalytic dehydrocondensation activation energies are calculated: Еact = 28.1 –28.5 kJ/Mole. As a consequence, for anhydrous caustic potash and platinum hydrochloric acid application as the catalyst activation energies are almost the same. It should be noted that in both cases formation of hindered compound of the following structure V: R O(SiPh2O)n R Si Si

O

O(SiPh2O)n

O

O(SiPh2O)m Si R

Si O(SiPh2O)m

R

Structure V

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171

by homo- and heterofunctional condensation reactions is eliminated [12–16, 25] due to steric hindrances and reaction proceeding in concentrated solutions. X-ray diffraction analysis indicates that the bead-shaped oligomers and copolymers are amorphous systems, and the interchain distance, d1, is increased with the volume of cyclic fragments.

Figure 1. The hydrogen liberation rate in dehydrocondensation reaction of 1,5-dihydride-1,5dimethyltetraphenylcyclotetrasiloxane with 1,5-dihydroxy- 1,5-dimethyltetraphenylcyclotetrasiloxane, where 1 – at 40°C; 2 – at 30°C; 3 – at 20°C (with KOH as the catalyst).

Table 1. Some physical and chemical parameters and the yield of bead-shaped structure polyorganosiloxanes, synthesized in catalytic dehydrocondensation

O(SiPh2O)nR x

H R

Si O

O(SiPh2O)mMe

O(SiPh2O)n

Si

Si

Yield, %

ηspec**

R

m

n

80 83 84 91 93 94 86 94 85 93 84 93 81 82

0,04 0,06 0,10 0,07 0,09 0,13 0,09 0,12 0,07 0,10 0,08 0,10 0,06 0,07

Me Me Me Me Me Me Ph Ph Me Me Ph Ph Ph Ph

1 1 1 1 1 1 1 1 2 2 2 2 2 1

1 1 1 1 1 1 1 1 1 1 2 2 1 2

Тreact, 0 С 20 30 40 20 30 40 40 40 40 40 40 40 40 40

Catalyst H2PtCI6 H2PtCI6 H2PtCI6 KOH KOH KOH H2PtCI6 KOH H2PtCI6 KOH H2PtCI6 KOH H2PtCI6 H2PtCI6

Тsoft, С 75-85 74-80 81-87 78-83 62-69 80-85 64-72 65-73 0

d1,Å 10,20 10,20 10,20 10,57 10,57 10,57 10,57

Si O H

Me

1 2 3 4 5 6 7 8 9 10 11 12 13 14

Copolymer

O(SiPh2O)m

№

*

Molecular masses were determined by the light scattering method. ** In toluene at 25°C.

M*ωx10-3 55 61 53 37

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Thermogravimetric studies of copolymers have shown that at 300°C mass losses do not exceed 3 – 6%, but are regularly increased with temperature. The main destruction process proceeds in the tem-perature range of 450 - 700°C and final mass losses increase with the volume of the cyclic fragment, respectively. Copolymers with cyclotetrasiloxane fragments in the backbone are characterized by higher thermal oxidative stability, than copolymers with cyclohexasiloxane ones, which is explained by variation of silsesquioxane (T) and siloxane (D) fragments. To synthesize cyclolinear bead-shaped polyorganosiloxanes, various HFC reactions in accordance with the following schemes are used [26]: branched sp a tia lly c ro ss-lin k e d p r o d u cts

NH2

H 2N R

R S h

4

Scheme 4. OH

HO R

R

+

R O

CI

CI R

R

R

x

Scheme 5.

OR

RO R

reaction term inated

R

Scheme 6.

It has been shown by gel permeation chromatography (GPC) and NMR methods that cyclolinear structure of the backbone of synthesized polymers is obtained at the interaction of dichlororgano-cyclosiloxanea and dioxy-derivatives in the presence of HCl acceptors only. The conclusion about cyclolinear structure of synthesized polymers is based on the data of hydrodynamic studies, MMD values and results of equilibrium rigidity determination. Cyclolinear structure of the backbone is also proved by NMR-spectroscopy method on 29Si nuclei. HFC reaction between 1,5-dichlorohexaorganocyclotetrasiloxanes and appropriate dihydroxyde-rivatives in the presence of hydrogen chloride acceptor has synthesized beadshaped cyclolinear organosiloxane polymers [27 – 31] in accordance with the general scheme as follows: R R

R R x

HO

R'

R'

+ x R' OH R

Scheme 7

R

R R R'

CI

R' O H

2xAc . HCI HO R' 2xAc CI R R

R R

2x

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173

Where: R=R’=Me, Ph; R≠R’ Applied difunctional organocyclotetrasiloxanes, both pure cis- and trans-isomers and their mixtures with isomers in various ratios, were of interest as model compounds for synthesizing stereo-regular poly(organocyclotetrasiloxanes) (POCS-4): trans-tactic, cis-tactic and with strict regular alternation of cis- and trans-sequences. Table 2. Physical and chemical parameters of POCS-4 of the structural formula as follows:

R' R R Si O Si O O O Si O Si R R' R n № 1 2 3 4 5 *

R

R’

Ме Me Ph Ph Ph

Ph Ph Me Me Ph

Isomeric composition, % cis trans 50 50 0 100 50 50 0 100 50 50

[η], dl/g 0,17 0,1 0,05 0,06 0,05

Тg,0С 0 +7 +43 +46 +220

Тmelt,0 С 100* 142* -

Data of X-ray diffraction analysis prove the presence of crystalline phase.

Applied difunctional organocyclotetrasiloxanes, both pure cis- and trans-isomers and their mixtures with isomers in various ratios, were of interest as model compounds for synthesizing stereo-regular poly(organocyclotetrasiloxanes) (POCS-4): trans-tactic, cis-tactic and with strict regular alternation of cis- and trans-sequences. For synthesizing POCS-4 (poly-1,5-dimethyltetraphenylcyclotetrasiloxane, poly-1,5diphenyl-tetra-methylcyclotetrasiloxane, poly(hexaphenylcyclotetrasiloxane) and poly(hexamethylcyclotetrasilo-xane) – PMCS-4), trans-1,5-dichlorohexaorganocyclotetrasiloxane and appropriate trans-dihyd-roxyderivatives, as well as several mixtures with different ratio of cis- and trans-isomers were used [27–29] in accordance with the scheme 7. Some physical and chemical parameters of polymethyl-phenylcyclotetrasiloxanes are shown in Table 2. PMCS-4 with different ratios of trans- and cis-sequences in the backbone possess one and the same glass transition temperature, and the crystallinity degree is lower that for PDMS. While polymeric chain is enriched by trans-units, crystallinity increases [27]. By methods of DSC, X-ray diffraction and thermooptical analysis, it have been detected that besides glass transition (Tg) and melting (Tmelt), polymers synthesized from monomers containing up to 95 – 100% of trans-isomers display a phase transition in the temperature range of 70 - 90°C, which is simulated as a transition from meso-morphous to isotropic state (Figure 2). Detection of thermotropic mesophase presence in PMCS-4 has induced different opinion on poly-organocyclosiloxanes), because heretofore poly(dimethylsiloxane) had been considered one of the most flexible-chain polymers. More thorough study of the spatial structure of PMCS-4, performed by 29Si NMR spectroscopy method, has shown that HFC

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reaction of 1,5-dichlorohexaorga-ocyclotetrasiloxanes with appropriate dihydroxy-derivatives proceeds (depending on selected condi-ions) with both preservation and inversion of isomers’ configuration. This made the authors to clear up the effect of such factors as the reaction temperature, acceptor basicity and solvent polarity in the HFC reaction on formation of different configurations of PMCS-4 units by 29Si NMR method.

Figure 2. DSC curve for trans-microtactic PMCS-4

Studied in ref. [26] is the effect of HFC reaction conditions on the configuration sequences in POCS-4. Since the mesomorphous state in PMCS-4 is formed in stereoregular trans-tactic polymers only [27, 32] and spatial configuration of initial monomers is not always fully preserved in poly-mers, the effect of HFC conditions on transformation of ≡SiCI and ≡Si-OH centers in initial com-pounds has been studied. The detected fact of cyclosiloxanes partial inversion at CI atoms substi-tution at silicon was expected, as reported before [33, 34]. More detailed description of reflex correlation was carried out in ref. [35]. Symbols and mark projections of units and bonds to the pla-ne perpendicular to the cycle plane. Thus, 29Si NMR spectra in PMCS-4 allow a conclusion about distribution of sequences from two units (tt, tc, (ct), and cc dyads) and the ratio of trans- and cis-units in the backbone. For these atoms, the following alternatives of spatial ringing are possible:

tt

tc

ct

cc

Figure 3. Alternatives of spatial ringing

and Symbols and mark projections of units and bonds to the plane perpendicular to the cycle plane. Correlation by reflexes from D fragments can be performed in the presence of reflexes from T-fragments of trans- and cis-units, calculated by ratios. Table 3 shows that low-polar D reflexes in the whole series are more intensive than high-polar ones. That is why the former reflex is related to trans-units.

Organosilicon Oligomers and Copolymers of Bead-Shaped Structure

175

Table 3. Conditions of synthesis, chemical shifts and intensities of reflexes in 29Si NMR spectra of PMCS-4 [35] Trans-/cis-isomer ratio in initial monomers Polymer, №

*

Relative intensity of δ Si reflexes for dyad units and sequences D Т

НС1 acceptor

In chloride

In diol

1

0.95/0.05

0.95/0.05

2

0.95/0.05

0.95/0.05

C5H5N

0.62

0.38

3

0.95/0.05

0.95/0.05

C5H5N*

0.63

0.37

4

0.95/0.05

0.95/0.05

(C4H9)3N

0.59

0.41

5

0.95/0.05

0.95/0.05

(С5Н11)3N

0.54

6

0.70/0.30

0.70/0.30

C5H5N

0.64

7

0.95/0.05

0.50/0.50

C5H5N

0.60

(C2Н5)3N

tc -65.47 0.11

ct -65.77 0.20

сс -65.68 0.01

0.61

0.18

0.19

0.02

0.31

0.35

0.33

0.02

0.17

0.42

0.32

0.03

0.46

0.15

0.41

0.40

0.04

0.36

0.40

0.22

0.25

0.13

0.40

0.32

0.25

0.27

0.16

-19.27

-19.31

0.80

0.20

tt -65.53 0.78

The acceptor represents solvent, simultaneously; in all other reactions, benzene, toluene or diethyl ether is used as solvents.

Data on intensities of reflexes in T-fragment spectra of PMCS-4 indicate that HFC reaction of initial dichlorohexamethylcyclotetrasiloxane induces different reflexes of CI atoms. These data contradict to the previously published results on dioxy- and dialkoxyderivatives, which indicate that the ring configuration does not change during the reaction [26, 28, 36], i.e. in spite of hydrolysis, in HFC reaction with appropriate dioxy-derivatives dichlorocyclotetrasiloxane is partly inverted. Data in Table 6 show that the inversion degree varies in a broad range and for units in the case of N(C2H5)3 acceptor equals 13%, and in the case of N(C5H11)3 is 88%. Though inversion and estimation of stereospecificity of HFC reaction require more thorough studies, already existing data indicate that the reaction represent the multi-stage process. At the first stage, interaction between dihydroxycyclotetrasiloxane and amine forms a structure. The second stage (the structure interaction) proceeds under different conditions with regard to the structure stability. In cases, when structures with amines of similar basicity are formed, their stability is approximately the same. However, depending on transitional amine structure, the attack may proceed from the front via formation of a trigonal pyramid. The first path proceeds via inver-sion of ≡Si-CI reaction center in the ring, and the second one via pseudo-rotation with the configu-ration preserved.

HO Me

Me OH

Me

k1 k2

H O

R R R

N

O

Me

H Nu

Scheme 8

N

R R R

176

O. Mukbaniani, G. Zaikov and T.Tatrishvili CI Me

Me

CI

Nu

+ Nu

Me

Me

Inversion CI . CI -NR3 HCI Me

Me O Me

OH Me

CI CI

Me Nu

Me

CI

Pseudo rotation

CI

-NR3. HCI Me

Me O Me

Me OH

Scheme 9

Table 4. Dependencies of the fracture of cis-units on the quantity of units, formed from dichlorohexamethylcyclotetrasiloxane, and the degree of inversion of dichloride units with regard to HCl acceptor used Polymer, No. 1 2 3 4 5

Acceptor (С2Н5)3N C5H5N C5H5N (C4H9)3N (С5Н11)3N

Fracture of cis- Degree of inversion of units units 0.17 0.13 0.36 0.34 0.67 0.69 0.81 0.84 0.84 0.88

As different configurations of the backbone units are formed from the same trans-isomers of initial dichloro- and dihydroxy-derivatives, the PMCS-4 chain configuration is generally regulated by chosen HCI acceptor. Studies of HFC reaction of 1,5-dichloro-1,5-diphenyl-3,3,7,7-tetramethylcyclotetrasiloxane with the appropriate dioxy-derivative in the presence of HCl acceptor by 29Si NMR spectroscopy method have indicates that reflexes from phenylsilsesquioxane Tfragment fall within the area of -79 ppm and are split into four components; reflexes from Dfragment are observed at -17 ppm and split into two components. If the same selection of HCI acceptors and solvents are used in HFC reaction, lower affinity of units from dichlorocyclosiloxane to inversion is observed (Table 6). While (C2H5)3N and С5Н5N acceptors are used, the inversion degree of ≡Si-CI centers in dichloromethylphenylcyclotetrasiloxane equals 4 – 6%, and for N(C4H9)3 acceptor - 30%. Reduction of inversion of ≡Si-CI centers in the ring, all other conditions being absolutely the same, may be associated with the effect of bulky phenyl substituting agent only, which renders difficulties to inversion of the reactive centers. For spatially hindered molecules of bi- and polycyclic structures, it is observed that substi-tution of CI atom at Si atom proceeds with preservation of the configuration [37]. The effect of tacticity of the polymeric backbone on properties of POCT-4 has been searched for [26]. Figure 4 shows curves for PMCS-4 with different backbone structure, obtained by the diffe-rential scanning calorimetry (DSC) method (curves 1 – 4). For atactic polymer the only transition, corresponded to Tg, is observed on curve 1, above which, in accordance with the data of X-ray dif-fraction analysis, the polymer is amorphous (two amorphous haloes at 2 θ = 8 – 11° and 20-35°). As the polymeric backbone is enriched with

Organosilicon Oligomers and Copolymers of Bead-Shaped Structure

177

tt-sequences (curves 2 – 4), additional phase transitions are observed. For different cooling rates and annealing temperatures, it has been observed that depen-ding on PMCS-4 enrichment by tt units the number of endothermic peaks and the temperature range between endoeffects from Тmelt to Тinv vary.

Figure 4. DSC curves for PMCS-4 (Table 2.3) of various stereo regular structure: 1 – atactic; 2, 2’ – transtactic polymer 2 (2- heating, 2’ – cooling); 3 – heating of polymer 3; 4—heating of polymer 4

Figure 5. Diffraction patterns for PMCS-4 (Table 6): a – polymer 2 at 12°С (1) and 74°С (2, 3); b - polymer 4 at 20°С (1), 86°С (2) and 96°С (3) (I, dimen- sionless units)

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Heating of trans-tactic PMCS-4 at 60 - 70°С induces gradual elimination of the greater part of ref-lexes, four of which only remain on the diffraction pattern already at 74°С (Figure 4). The character of 2d temperature dependence and correlation between angular positions of these reflexes allow a supposition that they relate to regulation in the basic plane of the rectangular cell with dimensions а=17.27 Ǻ and b=8.46 Ǻ. The first transition is not accompanied by significant variations in the basic plane package, but is associated with the loss of the farther translation order. Temperature in-crease above 74°C leads to elimination of low-intensive reflexes in angles (2θ =14 – 30°). Fusing of reflexes at 2θ =10 – 11° into a single one is observed on diffraction patterns in the temperature range of two following endothermal transitions (Figure 3, curve 2). This may testify about packing vari-ation in the basic plane. This effect is screened by isotropization (Figure 4). Final isotropization of polymer 2 proceeds at 110°C. Thus in spite of atactic PMCS-4, transition of trans-tactic PMCS-4 from crystalline to amorphous state is preceded by polymorphous transition of the mesophase II - mesophase I type. To obtain fuller picture on the cyclolinear polyorganosiloxanes tacticity effect on formation of crys-talline and mesomorphous states, by N.N. Makarova and her co-workers the PMPCS-4 and PPCS-4 were synthesized and their properties were studied.

Me

Ph

Me

Ph Ph O

Ph O Ph

Ph Me

Me PMPCS-4

Ph Ph PPCS-4

Figure 5 shows DSC curves for trans-PMPCS-4 and trans-PPCS-4. In spite of the aboveconsidered trans-PMCS-4, trans-PMPCS-4 displays lower crystallinity degree (~60%) at room temperature, though its saturation by tt-sequences is higher. As temperature increases, a single endothermal tran-sition at 197 - 202°C only is observed in it. In accordance with RSA data, this transition is associat-ed with polymer melting. Under different modes of annealing, cooling and repeated heating of PMPCS-4 sample, cold crystallization at 36°C and crystal II – crystal I transition at 119°C were ob-served. At 56 – 58°C, the DSC curve for PPCS-4 enriched with tt-sequences (Figure 5, curve 1) dis-plays the area of glass transition, and at 170-180°C– low endothermal effect with ∆Н =1,0 J/g. Com-paring data on RSA and DSC, the authors concluded that below 250°C PPCS-4 exists in the meso-morphous state. In accordance with the data of thermooptical analysis, isotropization of PPCS-4 is observed in the temperature range of 320 - 340°C, simultaneously with degradation of the polymer. More detailed description of PPCS-4 polymesomorphism and calculations of the cell parameters at chain packing in the basic plane are given in ref. [38]. Thus considered data on three POCS-4 possessing different spatial structures do not allow an un-ambiguous conclusion that enrichment of the polymer by tt-sequence units always causes occurren- ce of a mesophase, but hence, in the majority of cases the crystallinity degree is increased. Apparently, the data obtained should indicate that higher contribution to stabilization of the mesophases is provided by strong intermolecular

Organosilicon Oligomers and Copolymers of Bead-Shaped Structure

179

interactions; therefore, the side framing is the determining factor for realization of polymesophase transitions in cyclolinear POCS-4.

Figure 5. DSC curves for PPCS-4 (1) and PMPCS-4 (2)

The authors have also studied the effect of organic framing on properties of POCS-4 polymers. It is common knowledge that introduction of side groups of various origin causes changes in properties of linear poly(diorganosiloxanes) [39-42]. The above-mentioned data on PMCS-4 and PMPCS-4 show similar dependence of the phase states of polymers on the origin of organic substituting agents in POCS-4 polymers. That is why for better understanding of the influence of intermolecular inte-ractions on POCS-4 properties, poly(hexaalkylcyclotetrasiloxanes) (PACS-4) were synthesized [43]. Table 6 shows main parameters of PACS-4. Studies of PACTS properties by RSA method have shown that atactic PACS-4 with ethyl (PECS-4) and n-propyl substituting agents (PPCS-4) are not crystallized, but a single narrow reflex at 2θ=10-11° and amorphous halo at 2θ=20° are observed on the diffraction pattern in a broad temperature range. If methylsubstituting agent is changed by ethyl or propyl one, the narrow reflex is shifted towards low angles. The character of PACS-4 distribution image in the temperature range from Tg to 230°C for ethyl substituting agent and to 270°C for n-propyl one does not change. RSA data and clarification temperatures, Tcl, indicate that above Tg, atactic PACS-4 (except for methyl one) exists in the mesophase and transits to isotropic melt either at 220 - 230°C (as for PECS4) or at polymer degradation temperature (as for PPCS-4). Since for these polymers such factors as MM, MMD and tacticity of polymeric chain are close, one may conclude that occurrence and formation of the mesophase is stipulated by the increase of intra- and intermolecular interactions between alkyl substituting agents in cyclolinear polymeric chain. Table 6. Physical and chemical parameters and interchain distances of atactic POCS-4 № 1 2 3 4

R = R’ in POCS-4 СН3 С2Н5 n-С3Н7 С6Н5

Tg0C -51 -110 -55 +58

T cl00 280 300 >300

d1, Å 8.4 8.8 10.4 11.2

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O. Mukbaniani, G. Zaikov and T.Tatrishvili

Comparing phase diagrams of PACS-4 and linear polydialkylsiloxanes, one may easily observe general tendency of Tg and Tinv variation in organosiloxane polymers, for PACS-4 all temperature transitions being shifted towards higher temperatures [43, 44]. For polymeric chains from tt-sequences, analysis of PACS-4 structure, carried out on Stewart – Briegleb models, indicates a tendency of plane zigzag formation by the siloxane backbone, formed from intercyclic oxygen atoms [43]. Evidently, PACS-4 may be approximated by cylinders, diame-ters of which increase with the volume of alkyl substituting agent. Interchain distance, d1, indicated by X-ray diffraction data, varies from 8.4 (PMCS-4) to 10.4 Å (PECS- 4). Figure 4 shows a hypo-thetical model of POCS-4.

Figure 4. Hypothetical model of POCS-4.

Basing on the present model, one may suppose existence of a package representing somewhat peculiar packs of polymeric disks. However, for PACS-4, interchain distance, detected by the RSA method, is by 3.0 Å shorter than for the model suggested. In this connection, two variants are possi-ble: the first one suggests occurrence of second one drives rings to some angle to the main axis of the macromolecule. Figure 5 shows diagrams of the phase state of PMPCS-4 and PPCS-4. Contrary to PACS4, for PMPCS-4 clear dependence of temperature range of the mesophase existence on the number of phenyl substituting agents is absent. Apparently, irregular distribution of bulky substituting agents in cyclic fragment in every particular case introduces its own specific features. Among all the above-considered POCS-4, one polymer only possesses the mesophase obtaining it from the monomer - octaphenylcyclotetrasiloxane [38]. Summing up the data on POCS-4 phase transitions, unambiguous answer cannot be given, if side substituting agents stabilize the mesomorphous state of the polymer or not. Melting temperature of the polymer increases with the number of phenyl groups in the unit, and the range of existence of one- and two-dimensional regular structures is converged, because the initial degradation tempera-ture is about 300°C.

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The effect of POCS-4 molecular mass on the phase states is detected. Among works devoted to the study of MM effect on isotropization temperature variation, Tiso, in organic LC-polymers, the ones by Blumstein et al. should be outlined [45, 46]. These works show that Tiso increases with MM, for organic LC-polymers with mesogenic groups in the backbone in a quite narrow range of molecular masses.

Figure 5. Influence of the number of phenyl groups, N, in POCS-4 unit on phase transitions

Study of the molecular mass effect on the mesophase – isotropic melt phase transition, carried out for polydiethyl- (PDES) and polydipropylsiloxanes (PDPS), has shown that border values of Tiso are reached for PDES at the polymerization degree above 3,000 [42] and for PDPS at 600 [41]. For PMCS-4, the effect of molecular mass was considered for three samples. Data from Table 5 indicate that the mesophase - isotropic melt temperature transition occurs and reaches border values at much lower polymerization degrees. Data from works [29, 43] on Tiso variation for PACS-4 prove that border values by Tiso for these polymers are also reached at much lower molecular masses. For the purpose of studying the effect of cyclic unit on polymeric chain, the HFC reaction of 1,5-dichloroorganocyclopentasiloxanes with 1,5-dihydroxyorganocyclopentasiloxanes in the presence of hyd-rogen chloride acceptor and synthesized polyorganocyclosiloxanes (POCS-5) were studied in accor-dance with the scheme as follows [27, 36, 47, 48]: R R R'

+x

x CI

R' R

R

R

R

R R

R R

CI

OH

R'

R'

HO R

R

2xAc 2xAc .HCI

R R Scheme 10

HO

O

R'

H

R' R

R

R III

R 2x

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Where: R = R’ = Me [27], Et [47], n-Pr [47]; R ≠ R’; R = Me; R’ = Ph [48]. Forasmuch as neither of initial compounds was separated into spatial isomers (though the affinity to enrichment of a mixture of trans-isomers was observed), synthesized polymers possessed atactic structure. Table 6 shows physical and chemical parameters of synthesized POCS-5. Data of RSA and DSC in-dicate variations of Tg of POCS-5 analogous to PACS-4 with regard to the length of alkyl substi-tuting agents. However, the difference in Tg of PMCS-4 and PMCS-5 should be outlined, which equals approximately 20°C. Hence, Tg of PECS-4 and PECS-5 are equal (Table 6). Table 6. Physical and chemical parameters of POCS-5 Polymer, № 1 2 3 4 *

R in POCS-5

Yield, %

[η] 250С

Мn х 10-3

Тg, °С

Me Et* н-Pr Ph**

75 57 60 59

0.27 0.11 0.09 0.11

30.12 -

-72 -111 -80 -35

Тiso = 40 - 50°С. ** POCS-5 with methyl groups in organosilsesquioxane fragments partly substituted by phenyl ones.

All POCS-5, except for PECS-5, are amorphous above Tg; according to RSA data, PECS-5 is mesomorphous above Tg, which is proved by three narrow reflexes at 2 θ = 8.98°, 9.57° and 9.93°. This diffraction is preserved up to 40 -50°C. At this temperature on the DSC curve, termination of heat absorption is observed. For PECS-5, variations on the diffraction pattern at 20°C correlate well with the beginning of heat absorption on the DSC curve (Figure 6). At the same temperatures (5-20°C) texture disappearance is observed on a polarization microscope.

Figure 6. DSC curve for PECS-5 (1) and diffraction patterns at 50°C (2), 11°C (3) and 0°C (4) (I is separate units)

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For low-temperature phase of PECS-5, rectangular cell is the most probable in the basic plane; it is also probable 10°C above the transition point. Thus for PECS-5, which unit is represented by asym-metrical rings, formation of highly ordered crystalline as well as oneand two-dimensional ordered structures is hindered. However, due to intensification of intraand intermolecular interactions of or-ganic groups, conditions for overlapping between macromolecules may occur. Finally, introduction of polar groups may induce a mesogenic fragment to become more symmetrical. More representatives of bead-shaped cyclolinear polymers are POCS-6, backbones of which are composed of cyclohexasiloxanes. They differ from POCS-5 by inclusion of one more diorganosilo-xane fragment to the ring and the ratio between diorganosiloxane fragments to diorganosilsesqu-ioxane ones reaching the value of two. In spite of difunctional octaorganocyclopentasiloxanes, in the majority of cases, dichloro- and dihydroxy-derivatives of decaorganocyclohexasiloxanes are easily divided into cis- and trans-isomers, which gives an opportunity to obtain polymers with various se-quences in the configuration. HFC reaction of 1,7-dichlorodecaorganocyclohexasiloxanes with 1,7dihydroxydecaorganocyclohexasiloxanes mainly proceeds by the scheme as follows: R2 R2 x

R'

R'

2xAc HO OH -2xAc . HCI

+ x

CI

CI R2 R2

R2 R 2

R2 R2

R'

R'

OH

R' O

R'

R2 R 2

R 2 R2

Scheme 11

H 2x

Where: R = R’ = Me [27], Et [36], Ph [49]; R ≠ R’; R = Me; R’ = Ph [50]; R =Ph, R’ = Me [49, 50]. Synthesized in this HFC reaction were copolymers, completely soluble in usual organic solvents with [η] = 0.10 - 0.24. The authors of the works have studied the influence of HFC reaction conditi-ons on configuration sequences of synthesized polymer. 29Si NMR spectra of pure trans-isomers and mixtures with different ratios of cis- and trans-isomers have indicated that spatial configuration of initial monomers is not fully preserved, and in some cases, inversion of ≡Si-CI centers exceeds 50% [35]. Factors affecting variations in configuration of initial difunctional organocyclohexasiloxanes during HFC reaction were also studied by 29Si NMR analysis. By analogy, relation of reflexes in 29Si NMR spectra to spatial tt, ct, tc and cc configurations is based on the fact that fission of silses-quioxane atom may be stipulated by spatial isomerism of the back-bone components only. Data from Table 7 on PMCS-6 prove that HFC reaction in the presence of HCl acceptor (pyridine) proceeds with partial inversion of dichlorodecamethylcyclohexasiloxane, because three reflexes are detected in spectra. In the case of partial inversion of dioxy-derivatives, polymers 1 and 2 would contain all possible combinations of units, i.e. four reflexes of Tfragments. A series of experiments studying the effect of acceptor and solvent origins in the HFC reaction during PMCS-6 synthesis give results analogous to the ones, previously executed for PMCS-4. However, one more additional factor affecting on the inversion degree of the initial dichlorodeca-methylcyclohexasiloxane was observed: configuration of preceding unit in the backbone (configu-ration of dihydroxy-derivative). As trans-isomer of the initial monomer

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diol (Table 7) is used, the ratio of cis- and trans-units in the polymer becomes equal 0.72:0.28 from the initial one in dichloro-derivatives, which equals 0.52:0.48 [35]. Table 7. Conditions of synthesis, chemical shifts and intensity of reflexes in 29Si NMR spectra for PMCS-6 Polymer, №

1 2 3

Trans-/cis-isomer ratio in initial monomers In dichloride

In diol

0.52/0.48 0.52/0.48 0.52/0.48

1.00/0 0/1.00 0.52/0.48

Relative intensity of δ and Sequences D T -21.95 -67.60 0.28 0.23

Si

reflexes for dyad units

-67.63 0.35 0.23 0.23

-67.55 0.37 0.21 0.24

-67.58 0.56 0.30

Pure cis-dihydroxy-derivative was one of the initial products for synthesizing polymer 2, and units formed from dichloro-derivative preserved the configuration ratio, present in the initial monomer. Because minimal inversion equals 12 – 13%, it is quite probable that ≡Si-CI center is inverted not in the initial molecule of cyclic dichloride, but in oligomer composed of tt-sequences. This molecule consists of ~5 units (as shown below, equilibrium rigidity of trans-tactic PMPCS-6 is higher than that of atactic polymers). That is why for somewhat decrease of the backbone rigidity, one ≡Si-CI center is inverted in the HFC reaction starting from a definite length of oligomers at consecutive act of addition of initial diol or interaction of two oligomers (of any length). There are no grounds for considering inversion proceeding at the interaction of two initial organocyclohexasiloxanes only, as it has been suggested for PMCS-4. But simultaneously, there are no data disproving the supposition that the inversion proceeds at the stage of oligomerization. The latest results of synthesis of oligo-mers with strictly defined polymerization degree (three, five, seven repeated units) prove the case, when ≡Si-CI center is inverted as the end group in oligomers [51]. The effect of chain tacticity on the phase states of POCS-6 has been studied. On the example of two POCS-6 polymers, the influence of configuration sequences on thermal transitions has been investigated [52]. For this purpose, cis- and trans-isomers of 1,7-dihydroxydecamethylcyclohexasiloxane, 1,7-dichloro-1,7-diphenyl-3,3,5,5,9,9,11,11-octamethylcyclohexasiloxane and its pure cis- and trans-dihydroxy-derivatives were used. Polymers enriched with tc- and ct-sequences were synthe-sized by interaction of mixture of dichlorodecamethylcyclohexasiloxane cis- and trans-isomers with trans-diol (Table 8, polymer 1), cc-sequences being completely absent. Polymer 3 (Table 8), in which ttsequences were absent, was synthesized from pure cis-dihydroxydecamethylcyclohexasiloxane. Structures of polymers 1 and 3 are the following:

tt-tc (polymer 1)

tc-cc (polymer 3)

The image of sequences in the cyclolinear chain represents projections of cyclic units and bonds connecting them to the plane perpendicular to the ring plane. The structure of polymer

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185

1 is named trans-microtactic one, and structure 3 is cis-microtactic one. Atactic polymer 3 contained all types of tt, tc, ct and cc configuration sequences in approximately equal fractures. Four cyclolinear PBPCS-6 polymers of different structures were synthesized from pure cis- and trans-isomers of dichloro- and dihydroxyderivatives of diphenyloctamethylcyclohexasiloxanes: the first one is enriched with tt-sequences in the absence of cccombinations (trans-tactic polymer); the second one is enriched with cc-sequences in the absence of tt ones (cis-tactic polymer); the third one is mostly enriched with tc-sequences from cis-dichloro derivative and trans-diol (due to partial inversion of dichloride, ttsequences are present; that is why spatial structure of the third polymer is similar to the first one); the fourth one represents atactic polymer. Table 8. Some physical and chemical parameters of PMCS-6

№

Trans-/cis-isomer ratio in initial monomers

Yield, %

[η ] at 25°C,

Mesophase-isotropic melt transition Mx10

-3

Тmelt, 0 С

Тcl 0С

Тiso, 0 С

∆Hiso, kJ/mol

-91*

320

4.3

7.2

295-305

-

-91

310

5.4

-

270-290

0.15

-

-91

250

2.9

5.5

250-260

0.17

24.1

-91

294

4.6

8.1

220-240

In dichloride

In diol

1

0.70/0.30

1.00/0

71

0.15

46.0

2

0.55/0.45

1.00/0

79

0.24

3

0.40/0.60

0.03/0.97

76

4

0.50/0.50

0.50/0.50

80

dl/g

∆S, J/mol-deg

In the first two cases, tc-sequences are present in the NMR spectrum due to partial inversion of ini-tial dichloro-derivative. All polymers with different tacticity types displayed high yields, except for the polymer of cis-tactic structure, the yield of which is much lower due to intramolecular cyclizati-on reaction, which induces formation of tricyclosiloxane (in the case of methyl groups at silicon atoms). The phase state of PMCS-6 polymers of different tacticity were identified by the methods of DSC, RSA and thermooptical analyses. Figure 7 shows DSC curves for PMCS-6 polymers of various tac-ticity. Thermal characteristics of all transitions in PMCS-6 are shown in Table 8. Therefore, Tg is defined by chemical structure of the polymer unit and is independent of its spatial structure. The melting point is observed only for trans-microtactic PMCS-6 (polymer 1), the melting heat and, consequently, degree of crystallinity of PMCS-6 (polymer 1) being low. Above Tg, atactic and cis-microtactic PMCS-6 polymers exist in the mesomorphous state up to 300°C; trans-microtactic PMCS-6 polymer is the only one transiting into the crystalline phase above Tmelt. Such interpreta-tion of phase states is proved by RSA data. PMCS-6 diffraction patterns in the temperature range from Tg to 250 - 300°C displays a single nar-row reflex (1/2∆ = 20′) of high intensity at 2θ =0.5°, corresponded to the interchain distance. Opti-cal observations on a polarization microscope indicate that the polymers possess the birefringence property [32].

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Figure 7. DSC curves for PMCS-6 of different structures: 1 – atactic polymer; 2 – cis-microtactic polymer; 3 – trans-microtactic polymer.

In spite of PMCS-6, DSC curves of PMPCS-6 independently of the tacticity type of polymeric chain display additional endothermal transitions, induced by melting. Proceeding of PMPCS-6 crystalli-zation is proved by RSA data. The ability to crystallization of PMPCS6 samples depends on the co-oling rate, but the mesophase is formed in these polymers even at 300 deg/min cooling rate, and me-somorphous glass is formed below Tmelt. The mesophase – isotropic melt phase transition was de-tected for cis-tactic PMPCS-6 polymer only; the rest polymers remain in the mesophase in the temperature range from Tmelt to 300°C. Hence, it was concluded [27, 36, 50] that independently of dominance of one of the sequence types (tt, cc or ct) or they all exist simultaneously (atactic polymer), all POCS-6 polymers may exist in the mesomorphous state in a wide temperature range. Dependencies of Tg, Tmelt and Tiso on content of phenyl groups in PMPCS-6 polymers and copo-lymers are shown in Figure 8. The phase diagram of PMPCS-6 indicates that sequential substitution of methyl groups by phenyl ones causes a monotonous increase of Tg. Differences between Tg of PMCS-6 and linear PDMS polymer are low, and some increase of Tg reflects restrictions of the lo-cal mobility caused by the presence of cyclic sequences in the chain. Tg values of homopolymers and PMPCS-6 copolymers fall within the range, limited by glass transition temperatures of PDMS and PDPS polymers. All PMPCS-6 polymers possess the ability to crystallization. Values of Tmelt of PMCS-6 polymer fall within the range typical of PDMS melting. Introduction of phenyl substitu-ting agents increases Tmelt of PMPCS-6, which is the most abrupt at introduction of initial ones. Crystalline and mesomorphous phases in PMPCS-6 are identified with the help of RSA data, which prove the fact of their partial crystallization. Above Tmelt, all PMPCS-6 polymers and copolymers display the mesomorphous phase. The effect of molecular mass on occurrence of the mesomorphous phase in POCS-6 polymers is de-tected. Results displayed for POCS-6 polymers, in which configuration sequences of units alternate irregularly along the backbone, indicate that the ability to crystallization in them is disturbed. For the mesomorphous phase, strict regularity of units is not the necessary condition of its occurrence. In connection with the difference between studied POCS-6 polymers by the type of tacticity and mole-cular mass, the authors have separated effects induced by these two factors and detected more accu-rate, which type of configuration sequences creates conditions for mesophase stabilization.

Organosilicon Oligomers and Copolymers of Bead-Shaped Structure

187

Figure 8. Dependencies of Tg, Tmelt and Tiso on the quantity of phenyl groups N, in POCS-6 polymers

To study dependencies of POCS-6 translucence temperatures on molecular mass (MM), PMPCS-6 and PMCS-6 were fractioned, and molecular masses and isotropization temperatures of the fractions were determined [43,53, 54]. Data in Table 9 show that atactic PMCS-6 possesses the mesophase in all fractions. The isotropization temperature is decreased slowly first and then abruptly with the po-lymerization degree. Such type of Tiso dependence on MM of cyclolinear polymers is quite different from the analogous dependence for PDES [42] and PDPS [41], in which (as mentioned above) the ability to form the mesophase is observed at polymerization degrees as follows: P>200 for PDPS and P>500 for PDES. For fractioned PMCS-6 samples, isotropization heat and entropy are much higher and the tempera-ture range is much narrower, which may be induced by the solvent applied and conditions of sample precipitation during fractionation. A sharp dependence of Tiso on polymerization degree, mesophase occurrence in lowmolecular fractions, high values of Tiso and a broad range of mesomorphous phase existence are the indirect factors proving quite high equilibrium rigidity of atactic PMCS-6 polymer. Table 9. Description of PMCS-6 fractions Fraction №

[η], dl/g (25°С)

Μω

Polymerization degree

Тg, °С

Тg, °С

∆Нiso, kJ/mol

∆Siso, kJ/mol-deg

1 2 3 4 5 6,7 8 9 Non-fractioned sample

0.07 0.09 0.11 0.13 0.17 0.18 0.24 0.28 0.14

8250 8750 14400 16000 29000 34000 44000 76000 24000

19 20 34 37 67 79 102 176 61

-88 -88 -88 -89 -88 -89 -90 -89 -90

202 257 277 286 294 295 310 313 279

4.40 4.50 4.60 3.76 5.65 5.50 5.65 5.56 4.40

9.70 8.54 8.40 6.84 10.0 9.80 9.80 9.66 8.05

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The packing structure of POCS-6 chains in the mesomorphous phase is of special interest. Consider the structure and conformation of decaorganocyclohexasiloxanes unit on the Stewart-Brigleb models and compare with the temperature dependence of d1 reflex. Figure 9a shows a disk-like structure of the unit with d1=11.5 Å at the cycle layer thickness d1=7.8 Å. Disks combines in a chain form plates looking like the so-called sanidic mesophase [55] in organic LC-polymers. The height of POCS-6 macromolecule layer is close to that determined for PMCS-6 polymer (d1=8.4 Å). The presence of long-range order in the packing with the lower cohe-rence border at 400 Å indicates that packing types shown in Figures 9b and 9c are exclusively possi-ble at the current intermolecular distance (though similar distances are realized in the ring, too, ho-wever, so high long-range order cannot exist in them; moreover, temperature dependencies of inter-and intramolecular distances are different). The model suggested indicates presence of a single ma-ximum corresponded to the long-range order in one direction, perpendicular to the plane of the ring, which is the polymer backbone unit.

Figure 9. A hypothetical model of POCS-6 polymer unit (a), POCS-6 backbone fragment (b), and POCS-6 chain packing (c). Temperature dependence of interchain distance, d1, for mesomorphous component of PMCS-6 polymer (d) and typical diffraction pattern of POCS-6 in the mesomorphous phase (e) (I, dimensionless units)

Cyclolinear structure of synthesized POCS-4, POCS-5 and POCS-6 polymers was proved by hydro-dynamic study of properties of their solutions [56]. The expected results of these investigations should indicate the predominant influence of the equilibrium flexibility of macromolecules and other specific properties of polymeric chains in block on occurrence of the thermotropic mesophase in cyclolinear organosiloxanes. The polymers were fractioned into 8 – 14 components by coacervate extraction from the benzene – methanol system. For fractions and nonfractioned polymers, characteristic viscosities [η], were me-asured. Because that was the first example of studying conformations of macromolecules of this ty-pe in diluted solutions, authors of the work [56] paid much attention to selection of an equation, which would adequately describe hydrodynamic behavior of polymeric chains. Figure 10 shows de-pendencies of [η] on molecular mass (MM), represented in double logarithmic coordinates. Parame-ters of the Mark-KuhnHauvink equation for toluene medium at 25°C were determined from the slo-pe and disposition of the straight lines.

Organosilicon Oligomers and Copolymers of Bead-Shaped Structure

189

Figure 10. Dependence of lg[η] on ω lgM for: 1 – PMCS-5 polymer; 2 – PMCS - 4 polymer; 3 – PMCS - 6 polymer

Table 10. Conformation parameters of poly(organosiloxanes) Polymer

Unit structural formula

Me2SiO

PDMS

Me2

PMCS-4

Me

а*

Kuhn segment,А

References

0.5 - 0.8

10

[57]

0.71

29

[56]

0.64

23

[56]

0.78

38

[56]

0.98

80

O Me Me2

Me2

PMCS-5

Me O

Me Me2 Me2

Me2 Me2

PMCS-6

Me O

Me Me2 Me2

Me2 Me2

PMPCS-6 (atactic)

Ph

[26]

O Ph

1.16

115 [26]

O Ph

Poly(organo Silsesquioxanes)

*

Me2 Me2

Me2 Me2 Ph

PMPCS-6 (transmicrotactic)

In the equation [η] =ΚΜα

Me2 Me2

RSiO1,5

0.5-1.8

50 -130

[58 - 60]

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For some POCS conformation parameters and the value of the Kuhn segment A are shown in Table 10 are determined. Deviation of parameter a from 0.5 in this equation may be caused by volumetric effects in good sol-vents or partial hydrodynamic permeability of the coil, promoted by skeletal rigidity of macromo-lecules. Selection of a model for quantitative estimation of rigidity by these properties is usually complicated by the absence of reliable criterion, especially in the cases, when the value of parame-ter a falls within the range of 0.5 – 0.8. That is why to describe behavior of macromolecules in tolu-ene, the authors [56] have used the model of perturbed Gaussian non-permeable coil and the model of worm-like backbone.

Figure 11. Extrapolation by the Fixman-Stokmayer method: 1 - PMCS-6 polymer; 2 - PMCS-5 polymer

Figure 11 shows experimental dependencies of [η]/М1/2 on М1/2 for PMCS-5 and PMCS6 samples, parameters a of which are mostly different. As a consequence, conformation parameters and the va-lue of the Kuhn segment, A, values of which are shown in Table 10, are determined [57]. Found values of conformation parameters of these polymers indicate that equilibrium rigidity of macromolecules is increased with the size and symmetry of siloxane unit. Hydrodynamic behavior of PMCS-4 and PMCS-6 give no reason for corresponding these polymers to classic flexible chain ones [61]. Introduction of phenyl substituting agents to organocyclohexasiloxane unit increases ri-gidity of macromolecules (the Kuhn segment 80 A). As for trans-microtactic PMPCS-6, further on, the macromolecule rigidity is increased, which is comparable with rigidity of ladder poly(organosil-sesquioxanes) [58 –61]. Simultaneously, thermomechanical investigations were performed [28], obtained under continuous impact of compressing stress (100 g/cm3) on the sample in accordance with the technique [62]. Glass transition temperatures, shown in the Tables, are determined from the primary deviation of thermomechanical curve run in the area of positive deformations. Depending on the spatial structure of the cycle, synthesized atactic and syndiotactic polymers are characterized by almost equal glass transition temperatures, Tg. Thermogravimetric studies of synthesized polymers indicate different types of copolymers dest-ruction with due regard to substituting agents at silicon atom. For example, PMCS-4 methylsiloxane copolymer with regular alternation of dimethylsiloxane and methylsilsesquioxane units displays S-shaped curve of the mass loss, which reaches 98 – 99% at 650°C, and differential thermal curve dis-plays a single maximum. Determination of volatile degradation product composition under isother-mal conditions at 500-700°C has

Organosilicon Oligomers and Copolymers of Bead-Shaped Structure

191

indicated that polymethylbicyclosiloxanes and polymethyltricyclo-siloxanes of T2Dn and T4Dn composition (n=2, 3, 4) are main products of the process. However, be-sides polymethylcyclosiloxanes, D3 and D4 ones were detected, D4 content being below 3 – 4%. The data shown indicate degradation proceeding by the depolymerization mechanism. For copolymers containing diphenylsiloxane and phenylsiloxane units, the mass loss reaches 28 – 30% at 900°C, and DTA curves display three maximums at 490, 530 and 565°C. In the case of PMCS polymers, the composition of volatile degradation products displays benzene, methane and hexamethylcyclotrisi-loxane. At simultaneous presence of methyl and phenyl substituting agents, the composition of vo-latile products indicates more complicated proceeding of degradation. However, if formation of ben-zene and methane can be explained by radical-type Si-C bond break, D3 formation cannot be exp-lained in the frames of previously suggested depolymerizational mechanism due to formation of transient four-center complex [63, 64]. As shown in the literature, recently, a new type of polymers was synthesized which, besides three usual (solid, glassy and liquid) phases, display liquid-crystal and mesomorphous phases [65, 66]. Two types of thermotropic liquid-crystal polymers were of special interest, i.e. polymers with me-sogenic groups in the backbone and polymers containing mesogenic groups in comparatively short side chains. On the other hand, some polymers are known, capable of forming thermotropic meso-phase without mesogenic groups. Polydiethyl(propyl)siloxanes [67, 68] and polyphosphazenes [69] are the most wellknown polymers of these group. In this relation, the above-mentioned stereo regular cyclolinear methyl- and methyl-phenylsiloxane copolymers with different-size rings and framing groups in the macromolecular backbone are of special interest. Similar to poly(diethylsiloxanes) and poly(phosphazenes), meso-phases in cyclolinear organopolysiloxanes are formed in the absence of mesogenic groups, which makes representatives of this class quite interesting.

2. BEAD-SHAPED METHYLPHENYL(ETHYL)SILOXANE COPOLYMERS WITH ETHYLENE BRIDGES BETWEEN CYCLES Synthesis of carboorganosiloxane copolymers and polymers is based on hydride polyaddition of organohydrosiloxanes to organoalkenyl silanes [69]. Recently, this reaction is of great interest in the field of obtaining complex monomers [70], as well as in the field of study of addition mechanisms on various Pt, Pd, Co and metal carbonyl catalysts [71-74] and specificity of actions of one or other catalytic systems [75]. Besides carboorganosiloxane oligomers and linear polymers, other compo-unds were also synthesized by this method [76 – 78]. Discussed in the present chapter are synthesis and investigation results on properties of carbosi-loxane copolymers containing, besides organocyclotetrasiloxane fragments, organocyclopenta- and organocyclohexasiloxane fragments. The first cyclolinear organosiloxane polymer with ethylene bridges between rings was synthesized by hydrosilylation of 1-hydro-3-vinylhexamethylcyclotetrasiloxane. Hydrosilylation performed in CCI4 medium at 75°C in the presence of the Spire catalyst

192

O. Mukbaniani, G. Zaikov and T.Tatrishvili

(H2PtCI6x6H2O) has synthesized a poly-mer, viscous-flow at room temperature, in accordance with the following scheme [79]: Me Me nH

Vin

Me Me Vin

Me Me C2H4

H2PtCI6 H

Me Me Me Me

T0C

Me Me Me Me

Me Me Me Me

n-1

V

Scheme 12

Synthesized cyclolinear polymers consist of tetrasiloxane rings as elementary units, bound by ethy-lene bridges. It is found that hydrosilylation proceeds without breaking cyclotetrasiloxane ring and a low-molecular polymer with molecular mass M=2260 is synthesized in the reaction, well-soluble in benzene and other organic solvents. Besides the peak displayed by ≡Si-Me groups, the NMR spectrum possesses one non-splitted peak typical of ≡Si-СН2- groups with chemical shift (in relation to ≡Si-Me groups) equal δ = 0.35 ppm. Cyclolinear polymers were synthesized by hydrosilylation reaction of dihydridecontaining organo-cyclotetrasiloxanes with divinyl containing organocyclotetrasiloxanes [80]: Vin

Me Me Vin

R R' R' Me Me H H

Me R'

R

R R'

Vin

R=R'=Me (1a) R=Me; R'=Ph (1b) R=R'=Ph (1c)

R

Vin R' Me Me R' H R

R=R'=Me (3a) R=Me; R'=Ph (3b) R=R'=Ph (3c)

R R'

R

R R'

H Me

R=R'=Me R=Me; R'=Ph R=R'=Ph

(2a) (2b) (2c)

R=R'=Me R=Me; R'=Ph R=R'=Ph

(4a) (4b) (4c)

The polymers were synthesized by hydride polyaddition with 0.01N platinumhydrochloric acid-tetrahydrofuran solution as the catalyst. The catalyst concentration equaled 5x10-6 g per 1 mole of vinyl component in the temperature range of 60 - 150°C. It has been found that the reaction pro-ceeding at high temperatures displays formation of branched structures. The effect of initial mo-nomers’ structure on the formation rate of polymers, as well as on physical and chemical properties and structural features of synthesized polymers are traced. The reaction proceeds by the general scheme as follows [80]:

nH

H + n Vin 1

H2PtCI6

Vin 3

Scheme 13

Vin + nH

nVin 2

H

H2PtCI6

4 Scheme 14

C2H4 2n (Polymer D,F,G)

C2H4

2n (Polymer A,B,C)

Organosilicon Oligomers and Copolymers of Bead-Shaped Structure

193

The reaction proceeding was traced by viscosity increase of 1% polymer solution in toluene. It is found that at the same framing and under equal conditions rings possessing functional groups in 1,5-position enter the reaction of polyaddition at higher rate and form polymers with higher molecular masses. However, it has been observed that the rings with functional groups in 1,5- position are not only higher reactive, but also subject to side reactions. For example, soluble polymer A is formed at 60°C only, polymer B – at 60 - 70°C, and already at 120°C branching proceeds. For polymer C, the loss of solubility is observed at temperature above 80°C. Polymers D, F and G can be easily syn-thesized at 50 - 80°C, and the loss of solubility is not observed in this case. Table 12 shows some physical and chemical parameters of cyclolinear polymers with ethylene bridges bonding rings. Table 12. Some physical and chemical parameters of cyclolinear polymers with ethylene bridges bonding rings №

Initial monomers

Reaction temperature,

η

spes

3

m /kg

°C

1 2 3 4 5

6 *

2a+4a (R=R’=Me) 1a+3a (R=R’=Me) 2b+4b (R=Me, R’=Ph) 1b+3b (R=Me, R’=Ph) 2c+4c (R=R’=Ph) 1c+3c (R=R’=Ph)

[η ]⋅ 10

Мх10-3 Light By ≡Si-H Scattering groups,%

80 60 60 150 60 100 100

0.06 0.12 0.12 0.26 0.12 0.16 0.09

0.08 0.14 0.12 0.22 0.12 0.07

67 100 200 616 154 53

53 142 108 48

100 150 180 100

0.12 0.22 0.25 0.04

0.13 0.04

51 172 250 7

40 6.5

Polymer

А D B F C

G

At 25°C in toluene.

As follows from the data shown, that soluble polymer A is synthesized at 60 and 100°C, and already at 120°C branching processes are observed. There are data in the literature indicating that as heated with silicones [81] and silanes [82], catalysts from the platinum group are capable of detaching methyl or phenyl group at the catalyst concen-tration from 0.01 to 1%. Spire et al. [83] has observed detachment of methyl group at hydride addi-tion of bis(trimethylsiloxy)methylsilane to hexane-2 at 50°C and Н2РlСl6x6Н20 concentration equal 5×10-5 mole per vinyl group. It is shown [79] that as heated with polymer 4a under the reaction con-ditions, platinum-hydrochloric acid does not detach methyl group, and the ring does not enter reg-rouping or disproportionation reaction. Possible side reactions were estimated by GLC and 1H NMR-spectroscopy methods. The study of thermal oxidative degradation of synthesized polymers at heating with the rate equal 5 deg/min indicates that the temperature of decomposition beginning of polymer depends on the origin of framing groups. Polymers A and B, which contain methyl groups only, begin degrading at 250°C independently of molecular mass within its range from 6×104 to 2×105. Substitution of a part of me-thyl groups by phenyl ones induces the increase of the initiation temperature of decomposition up to 350 - 370°C, which is associated with increased

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resistance of phenyl groups to oxidation, as well as their inhibiting effect of methyl groups on oxidation [84]. Besides 1,5-divinyl(dihydride)-1,5-dimethyltetraphenylcyclotetrasiloxane, the authors [85] have us-ed 1,5-divinyl(dihydride)-1,5-dimethylhexaphenylcyclopentasiloxane and 1,7divinyl(dihydride)-1,7- dimethyloctaphenylcyclohexasiloxane as initial compounds in hydride polyaddition reaction, by which cyclolinear organosiloxane copolymers with ethylene bridges between rings containing orga-nocyclotetrasiloxane, organocyclopentasiloxane and organocyclohexasiloxane fragments are synthe-sized. As the catalyst for polyaddition, 0.01 M solution of platinum hydrochloric acid in tetrahydrofuran was used. Polyaddition proceeds in argon at equimolar ratio of initial substances (1:1) in the absence of solvent and in the temperature range of 75 - 115°C. It is found that the above-mentioned con-ditions do not induce scission of the siloxane ring. As a consequence, hydride polyaddition under se-lected conditions proceeds in accordance with the scheme as follows [85 - 87]:

Ph2 Ph2 O(SiO) O(SiO) Me Me Me m Me k 0 Si Vin Cat., T C Si H + x Vin Si x H Si O(SiO)n Ph2

O(SiO)l Ph2

Ph2 Ph2 O(SiO) O(SiO) Me Me Me Me k m Si Si CH2CH2 Si Si CH2CH2 O(SiO)n Ph2

Scheme 15

O(SiO)l Ph2

x

where k = n = m = 1, l = 2 (VI); k=n=1, m = l = 2 (VII); k=m =1, n = l = 2 (VIII); k = 1, n = m = l = 2 (IX); k = n = m = l = 2 (X). Copolymers with ηspec = 0.13 - 0.18 representing slightly yellow glassy like transparent products, which are soluble in usual organic solvents, were synthesized in the reaction. The reaction pro-ceeding was traced by the increase of 1% toluene solution viscosity (Figure 12). It has been found that viscosity growth rate is increased with temperature increasing from 95 to 115°C, and increase of the cyclic fragment volume induces deceleration of the viscosity increase. 1 H NMR spectral studies display that polyaddition mainly proceeds by the Farmer rule with formation of dimethylene bridges between cyclic fragments. Copolymer 1 (Table 13) displays a complex multiplet in the range of 6.9 - 7.6 ppm typical of protons of phenyl groups, and the reflex centered at 0.28 ppm belongs to protons of methyl group. The reflex with chemical shift at 0.32 ppm is corresponded to protons of methylene group (-CH2-CH2-). Moreover, the spectrum displays reflexes from protons of non-reacted vinyl groups (a complex multiplet in the area of 5.6 – 6.1 ppm) and ≡Si-H groups (at 4.4 ppm). The spectrum also displays a doublet reflex with chemical shift centered at 1.05 ppm, which may be related to methyl protons in =СН-СН3 group with the quantity below 8%.

Organosilicon Oligomers and Copolymers of Bead-Shaped Structure

195

Table 13 shows some properties of carbosiloxane co-polymers with cyclic fragments in the back-bone.

Figure 12. Variation of optical density of ≡Si-H bond and specific viscosity with time by reaction (17): 1 and 1’ – copolymer 4 (Table 13) at 75°C; 2 and 2’ – for copolymer 1 at 95°C; 3 – for copolymer 1 (Table 13) at 115°C

Table 13. Some physical and chemical parameters and yields of copolymers (VI-X) containing cyclotetra(penta, hexa)siloxane fragments in the backbone № k

n

m

l

1

1 1 1 2 2 2 2 2

1 1 2 1 1 1 2 2

2 2 2 2 2 2 2 2

2 3

4 5

1 1 1 1 1 1 1 2

Yield , % 94 95 91 90

92 90

Reaction temperature, 0 C 95 115 115 75 95 115 95 115

ηspe

Тsoft,0 С

d1,Ǻ

Mnx10-3

0.15 0.18 0.16 0.11 0.14 0.18 0.10 0.11

48-50 51-54 43-46 45-48 42-44 39-41

9.40 9.50 9.50 9.72

97 87 51

The copolymers were thermogravimetrically studied with the help of Seteram Co. thermoweighing machine B-60 in argon (at the heating rate of 5 deg/min) with simultaneous selection and analysis of gaseous degradation products, and the effect of introduction of bulky cyclic fragments into the back-bone on their thermal stability was traced. Figure 13 shows the investigation results indicating that initial mass losses are observed at 280 - 350°C depending on the volume of cyclic fragments in the chain. In the temperature range of 400 - 450°C hydrogen and methane are liberated, which is caused by ≡Si-C and С-Н bond break and leads to cross-linking by methyl and phenyl groups [88, 89]. Similar effect is also observed at thermal degradation of both carbosiloxane [90] and organosiloxane copolymers [90]. Degradation proceeds by the radical mechanism with formation of oligomeric products [91, 92].

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Figure 13. Thermogravimetric analysis of cyclolinear carbosiloxane copolymers.

This gives an opportunity to suggest [86, 87] that besides the backbone break, radical cross-linking reactions by methyl and phenyl groups proceed at thermal pyrolysis of carbosiloxane copolymers, which is also accompanied by liberation of hydrogen, methane and other low-molecular organic compounds of benzene and other types. Above 600°C, breakthrough of the mass loss curves hap-pens. Final mass losses fall within the range of 34 – 38%. Thermomechanical studies have indicated that the glass transition temperature of synthesized copo-lymers is decreased as the volume of cyclosiloxane ring in the chain is increased. The results of X-ray structural analysis indicate that the copolymers represent amorphous systems, and increase of cyclic fragment volume leads to an insignificant increase of the interchain distance. To detect the effect of the size of cyclosiloxanes, cross-linking bridges between them and deli-mitation of their roles in ability of polymers to self organize as mesomorphous structures, investi-gators [93] have studied polyaddition of dihydroalkylcyclotetra(hexa)siloxanes to divinylorgano-cyclotetra(hexa, octa)siloxanes in the presence of different complex platinum catalysts (dicyclo-pentadienylplatinum dichloride, the Carsted catalyst) and their reduced forms by the scheme as follows: R x H

O(R2SiO)n Si

R

R

O(R2SiO)n

R Pt x Si + Si Si O(R2SiO)n H H2C CH O(R2SiO)n CH CH2 Scheme 16

O(R2SiO)n R

R Si

Si CH2 CH2 O(R2SiO)n

2x

Where: n = 1 - 3, R = Me, Et. All synthesized polymers are completely soluble in usual solvents. The effect of platinum colloid forms used in polyaddition reaction on molecular structure of synthesized cyclolinear polyalkylcar-bosiloxane polymers has been studied. In accordance with the opinion [93], application of plati-num-hydrochloric acid [80] to polyaddition of dihydromethyl-

Organosilicon Oligomers and Copolymers of Bead-Shaped Structure

197

phenylcyclotetrasiloxanes to divinyl-methylphenylsiloxane induces side reactions, which disturbs the regularity. This is proved by dis-crepancy between molecular masses and viscosity parameters. The possibility of side reactions pro-ceeding in the case of polyaddition is indicated in the work [94]. Taking into account the data obtained [85-87, 93-96] for the synthesis of cyclolinear alkylcarbosilo-xanes, special attention was paid to determination of optimal reaction conditions of polyaddition [93], in particular, selection of a catalyst providing for formation of polymers of strict cyclolinear structure. Formerly, Levis [97] has found that hydrosilylation proceeds with high efficiency on platinum complexes, reduced to the colloid form. Preliminary results show that polyaddition of 1,5-dihyd-rohexaethylcyclotetrasiloxane to 1,5-divinylhexaethylcyclotetrasiloxane on reduced CPDP in the form of colloid platinum decreases polydispersion degree of carbosiloxane polymer from 8.21 to 10.3. Taking into account encouraging results of the work [96], a sequence of cyclolinear carbo-siloxane polymers were synthesized [93] in the presence of three different forms of platinum cata-lysts, introduced into the reaction mixture after preliminary formation. Table 14. Some parameters of cyclolinear poly(alkylcarbosiloxanes) with regard to synthesis conditions Polymer №.

1 2 3 4** 5 6 7 8 9 10 11 12 13 14 *

R

n

Ме Ме Ме Et Et Et Me Me Me Et Et Me Me Me

1 1 1 1 1 1 2 2 2

Reaction conditions Reaction Time, Catalyst* Temp.,°C hour

NRF YC BC NRF YC BC NRF YC BC NRF YC NRF YC BC

70 70 70 70 70 70 25 25 70 130 130 70 70 70

1 1 20 10 20 47 168 144 50 9 10 10 10 10

[η]

0.31 0.21 0.12 0.08 0.15 0.08 0.80 1.30 0.13 0.14 0.24 0.12 0.14 0.06

Μ ωx10 -3

Μ ω/Μn

Μz /Μ ω

46.0 49.5 26.0 322.1 462.2 29.0 50.9 67.3 46.9 34.0 21.0

-

-

4.34 3.10 10.1 7.10 2.08 13.7 3.30 -

2.81 2.40 6.27 5.20 1.72 6.51 2.20 -

NRF is the non-reduced form of dicyclopentadienyl-platinum dichloride (CPDP); YC is the yellow colloid of CPDP; BC is the black colloid of CPDP. **After 10 hours polymer transforms into the cross-linked form. ***Polymers represent cyclolinear carbosiloxane copolymers with regular alternation of decamethylcyclohexasiloxane and tetradecamethylcyclooctasiloxane fragments. **** In toluene 250С dl/g.

Table 14 shows that the form of platinum compounds display different catalytic activities. Usually, yellow colloid form is more active compared with the black one, but lower polydispersion degrees are typical of polymers, synthesized in the presence of the latter one. As a consequence, the use of black colloid for obtaining polymers of regular structure is optimal, though due to low catalytic activity of it either high temperature of the reaction or

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high reactivity of initial reagents is required, which, for example, takes place for polymer 9 (Table 14). For synthesized carbosiloxane polymers, MMD curves were determined by the gel permeation chro-matography (GPC) method. Table 14 shows Мω, Мω/Мn and Мz/Мω values for polymers with dif-ferent sizes of cyclic fragment, from cyclotetrasiloxane to cyclooctasiloxane. Data on MMD (Table 14) indicate that cyclolinear polymers with the most homogeneous structure and composition are formed on the reduced catalyst. The more so, every particular case displays its own optimal type of the reduced form, i.e. catalytic system for synthesizing cyclolinear polymers should be selected with regard to activity of dihydrorganocyclosiloxane in polyaddition reaction. It should be noted that as yellow colloid is applied as the catalyst, the reaction temperature has no ef-fect on the shape of MMD curves for ethyl-substituted polymers with tetra- and hexasiloxane cyclic fragments. Cyclolinear structure of synthesized polymers is proved by the results of NMRspectroscopy studies. For all polymers independently of MMD, 29Si NMR spectra display two groups of reflexes in the area of -20.0 – 23.0 ppm, corresponded to atoms of silicon in R2SiO and RSiCН2CH2 groups (Table 14). Reflexes typical of silicon atoms in the branching centers are absent. The quartet of reflexes from RSiCH2CH2, observed in 29Si NMR spectra of polymers №8 and 9 (Table 14) confirms atactic structure of synthesized products. Analysis of NMR spectra of polyaddition products indicates that the reactions proceed by the Farmer rule forming CH2-CH2 bridges between rings in more than 95% of cases. By the methods of differential scanning calorimetry (DSC), X-ray structural analysis (RSA) and op-tical microscopy, parameters of thermal transitions in synthesized cyclolinear polymers with diffe-rent structures of units, MM and polydispersion degree were determined. Table 15 shows that Tg of all other polymers are higher than Tg of cyclolinear siloxane polymers, but this difference is decreased with increase of the quantity of diorganosiloxane groups in cyclosiloxanes. Regularities observed for Tg shift with variations of the cyclosiloxane size and length of side substituting agents of carbosiloxane polymers are similar to these, previously detected for pure cyclolinear polysiloxa-nes at analogous variations of the chemical structure [49]. Independently of molecular mass and polydispersion degree, all cyclolinear carbosiloxane polymers with cyclic tetrasiloxane fragments (Table 15, polymers №1-6) and the ones with decamethylcyclo-hexasiloxane fragments (Table 15, polymers №7-9) do not display mesomorphous properties. RSA data (Figure 14) indicate that polymers №2 – 9 are amorphous, because their diffraction patterns are similar by type to these of amorphous polyorganosiloxanes. They contain two amorphous halos: symmetrical intensive one at 2θ (∆1/2 =1.8°) and diffuse low one at 2θ. Distribution of amorphous scattering intensity, in particular, angular 2θ position, depends on the sizes of cyclic fragment and side substituting agent (Figure 14). Because compounds representing the mixture of cis- and trans-isomers were used in polyaddition reactions, carbosiloxane polymers should possess the atactic structure. Such conclusion is also pro-ved by the above-mentioned NMR spectra data. In this connection, the absence of ability to crystal-lize in the majority carbosiloxane polymers is quite explainable. However, the absence of mesomor-phous properties in polymer with decamethylcyclohexasiloxane fragments is the unexpected result. The case is that at the polymerization degree P≥5, atactic non-crystallizing cyclolinear polyorganosi-loxanes with

Organosilicon Oligomers and Copolymers of Bead-Shaped Structure

199

decamethylcyclohexasiloxane fragments are mesomorphous, temperature range of mesophase existence increasing with molecular mass (MM) [56]. It should be noted also that the average intermolecular distance d1≈8.3 Å for polymers №.7-9 (calculated from 2θal) is practically coincident with the similar value d1≈8.6 Å for amorphous cyclolinear poly(organosiloxanes) with decamethylcyclohexasiloxane fragments [98]. The latter are characterized by the polymerization degree, P, below 5. Comparison of the above-shown data on cyclolinear carbosiloxanes with pre-viously published results on the phase structure of cyclolinear organosiloxane homo- and copoly-mers [99] indicates that introduction of different groups between cyclic siloxanes (flexible junc-tions) causes a significant decrease of isotropization temperature.

Figure 14. Diffraction patterns: a – polymer № 3 at 20°C (1) and 73°C (2), polymer №9 at 20°C (3), copolymer № 12 at 20°C (4); b –polymers №6 (1) and 11 at 20°C (2)

At some critical distance between cyclic rings in considered carbosiloxane copolymers, as well as in cyclolinear siloxane copolymers [48, 100], the ability of molecules to form the mesomorphous phase is suppressed: above Tmelt, crystallizing copolymers transit into the melt, and non-crystallizing ones are amorphous in the whole temperature range. For example, copolymers with –R2SiO- junction pre-sserve mesomorphous properties, whereas copolymers with O(СН3)2SiСН2СН2Si(СН3)2O, R2SiO)2 and -СН2-СН2- junctions lose these properties. There is another fact of special interest, which may affect the mesomorphism of copolymers: lower flexibility of -CH2CH2- groups compared with oxy-gen. By increasing the elementary unit to tetradecamethylcyclooctasiloxane, an attempt was made [93] to change the ratio of distances between rings and junctions. Carbosiloxane copolymers №12-14 with regular alternation of decamethylcyclohexasiloxane and tetradecamethylcyclooctasiloxane fragments

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O. Mukbaniani, G. Zaikov and T.Tatrishvili

in the chain was synthesized by polyaddition on different non-reduced and reduced colloid forms of the CPDP catalyst (the attempt to synthesize dihydrotetradecamethylcyclooctasiloxane has failed [101]). Table 15. Calorimetric and structural parameters of cyclolinear carbosiloxane copolymers Polymer*, №. **

*

Тg,°С

Тmelt, °С

2θ, deg

Chemical shifts Si 29Si NMR, ppm R2SiO

RSiCH2CH2

2

-30

42

12.0

-18.99

-19.14

6

-74

-

13.0

-20.85

-20.22

9

-69

-

10.6

-21.76 21.77

11

-104

220***

9.80

-22.95

13

-75

-

9.37

-

-21.59 -21.61 -21.66 -21.69 -23.62 -23.69 -

Polymer numeration in accordance with Table 14. Isotropization temperature.

**

Melting heat Qmelt = 167.6 J/mol.

***

Thus, substitution of oxygen bridges between cyclic fragments by -СН2СН2- groups leads to the loss of the ring ability to intra- and intermolecular correlations and, consequently, to the loss molecule ability to self-organization and formation of mesomorphous structures. Introduction of ethyl substi-tuting agents at hexasiloxane rings form additional intra- and intermolecular interactions, due to which the ability of macromolecules to self-organization occurs.

3. OLIGOMERS AND COPOLYMERS WITH ORGANOCYCLOCARBOSILOXANES FRAGMENTS IN THE CHAIN To synthesize oligomeric organocyclocarbosiloxanes, the reaction of dihydroxyorganocyclocarbo-siloxane homofunctional condensation in 60% toluene solution was studied [102] on the Dyne–Stark device both in the presence (7%) and in the absence of activated coal. As a consequence, dihydroxy-containing organocyclocarbosiloxanes oligomers were synthesized in accordance with the scheme as follows [102, 103]: C2H4 Me m HO Si Si OH O O Si Ph2

C2H4 Me Si Si O H O O Si m Ph2 XI

Me

Me

-H2O Scheme 17

HO

Organosilicon Oligomers and Copolymers of Bead-Shaped Structure

201

where: m = 8, 11. Organocyclocarbosiloxane oligomers obtained represent solid products, well soluble in various or-ganic solvents. It is found that “non-equilibrating” catalyst which is activated coal, used in homo-functional condensation, does not induce scission of the organocyclocarbosiloxane ring. X-ray diffraction analysis indicates that oligomers are amorphous systems with the interchain dis-tance equal d1≈8.64 Å. Thermogravimetric studies show that by thermal oxidative stability oligo-mers are behind polyorganocyclotetrasiloxanes only. For the purpose of synthesizing organocyclocarbosiloxane oligomers and polymers with different ratio of SiO/SiC groups in the complex repeated unit and studying the effect on their ability to self-organization in bulk and in ultra thin films, HFC reaction of dihydroxymethylcyclosiloxalkanes with dichloromethylcyclosiloxalkanes proceeding in the presence of pyridine acceptor in accordance with the scheme as follows was studied [104]: Me Me Me (CH2)n (CH2)n 2mPy HO mHO Si Si OH + mCI Si Si CI - 2mPyHCI O O O O Si Si Me Me Me Me Me

Me (CH2)n Si Si O H

Me

O

O Si

Me

Me

m

XI

Scheme 18

Where: n = 2, 3; Me

Me2 Me2 OSiCH2SiO

Me

Me2 Me2 OSiCH2SiO SiOH

SiCI + HOSi

xCISi OSiOSiO Me2 Me2

Me

Me

OSiOSiO Me2 Me2

Me

Scheme 19

2xPy HO -2xPyHCI

Si

Me2 Me2 OSiCH2SiO Si O H OSiOSiO Me2 Me2 Me 2x XII

Composition and structure of synthesized oligomers is proved on the basis of the ultimate analysis and by IR, 1Н and 29Si NMR spectral data. Spectral data (oligomers №1–3, Table 2.18) indicate that the presence of cis-trans, trans-trans and trans-cis combinations of rings in the polymer chain is si-milar to polydecaorganocyclohexasiloxanes [26]; in the case of transdihydroxyorganocyclohexasi-loxane, cis-cis-combination in the polymer chain is absent. They display atactic structure of cycloli-near chain, enriched with trans-trans-sequences.

4. SILARYLENE CYCLOSILOXANE AND SILARYLENE CARBOORGANOCYCLOSILOXANE OLIGOMERS AND COPOLYMERS Introduction of phenylene unit into the polyorganosiloxane chain causes a significant variation of the chain configuration and flexibility, which affects physical and chemical parameters of the po-lymer. Moreover, different combinations of linear ≡Si-O-Si≡ or silarylene fragments with cyclic on-es may change conformational flexibility of the chain

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O. Mukbaniani, G. Zaikov and T.Tatrishvili

[105]. As indicated [106, 107], the origin (chemical and geometrical) of substituting agent at the atom of silicon may induce increased chain rigidity, if substituting agents between siloxane chains are composed of -СН2-СН2- and ≡Si-C6H4-Si≡ fragments [108, 109]. For the purpose of synthesizing dihydroxy-containing silarylene cyclosiloxane oligomers, HFC reac-tion of 1,4-bis(chlorodimethylsilyl)benzene, synthesized by the known technique, with 1,5-dihyro-xyhexaphenylcyclotetrasiloxane and 1,7dihydroxydecaphenylcyclohexasiloxane was studied [87, 110 – 112] at the molar ratio of reagents as follows: 1:0.9, 1:0.95 and 1:1, respectively. The reaction proceeded in 60 - 70% solution of anhydrous toluene in the presence of pyridine, the acceptor of hydrochloric acid, at room temperature with consequent boiling of the solution up to the boiling point of the solvent used. Generally, the reaction proceeds by the scheme as follows: O(SiPh2O)k Ph Me Ph x HO Si Si OH + yCI Si Me O(SiPh O) 2

k

Ph HO

Me

2yPy

Si CI Me

-2yPyHCI

O(SiPh2O)k Ph Me Si Si O Si

Me

Me O(SiPh2O)k Scheme 20

Me

Si O

H m

where: k = 1 (XIII), 2 (XIV); m = 4 – 16. The HFC depth can be varied by changing the ratio of initial components. Equimolar ratio of the ini-tial components gives maximal depth of HFC reaction. After partial overprecipitation by methanol from toluene solution, synthesized oligomers become yellow or light-brown transparent products, well-soluble in various organic solvents. Some parameters of the oligomers are shown in Table 16. Silarylenecyclosiloxanes of structure XIV with higher molecular mass were synthesized by catalytic dehydrocondensation of 1,7-dihydride-1,7-dimethyloctaphenylcyclohexasiloxane and 1,4-bis(hydro-xydimethylsilyl)benzene [111, 112]. For the purpose of synthesizing silarylenecyclohexasiloxane copolymers, catalytic dehydroconden-sation of 1,7-dihydride-1,7-dimethyloctaphenylcyclohexasiloxane with 1,4bis(hydroxydimethylsi-lyl)benzene, at different temperatures (30, 40 and 50°C) in the solution of anhydrous toluene (C= 0.4686 mol/l) in the presence of powder-like caustic potash has been investigated. Recently, it has been shown that during catalytic dehydrocondensation of linear α,ω-dihydridediorganosiloxanes with α,ωdihydroxydiorganosiloxane in the presence of caustic potash, depending on the length of siloxane fragments, both individual organocyclosiloxanes and linear copolymers are synthesized [113]. Besides, it was shown that during catalytic dehydrocondensation of dihydrideorganocyc-losiloxanes with dihydroxyorganocyclosiloxanes in the presence of nucleophilic anhydrous potas-sium hydroxide, the break of cyclosiloxane rings does not take place [114]. Dehydrocondensation reaction proceeds according to the following scheme [111, 112,114]:

Organosilicon Oligomers and Copolymers of Bead-Shaped Structure

Me

O(SiPh2O)2 Me Me Me x HO Si Si OH + x H Si Me O(SiPh O) 2

Si H Me

2

T0 C (x-1)H2 Me

O(SiPh2O)2 Me Me Me H O Si Si O Si Me O(SiPh O) 2

203

Si

H

Me m

2

Scheme 21 where: T = 30, 40, 50°C. During catalytic dehydrocondensation of 1,7-dihydrideorganocyclohexasiloxane with l,4bis(hyd-roxydimethylsilyl)benzene in the presence of potassium hydroxide, the reaction order, rate constants and activation energy were determined. Catalytic dehydrocondensation is the second order reaction. Some physical and chemical parameters of low-molecular copolymers are shown in Table 16. Table 16. Yield and physical and chemical parameters of α,ω−dihydroxysilarylenecyclo(tetra)hexasiloxanes №

m

ηspec

XIII

Yield, % 76

4

0.04

1

XIII

81

6

0.04

1

XIII

85

16

0.06

2

XIV

80

4

0.04

2

XIV

86

12

0.05

7*

2

XIV

93

13

0.08

8*

2

XIV

93

-

0.09

9*

2

XIV

95

16

0.09

Oligomer structural unit

k

Structure

1

Me Si

1 2 3 4 6

*

Ph2 O(SiO) k Ph Me Ph O Si

Si O Si O(SiO)k Ph2

Me

Me

m

Тg,0 С 5561 6165 6368 6165 6771 6165 6466 6771

d1,Å 9.98 10.04 10.08 10.04 10.04

The oligomers were synthesized by dehydrocondensation reaction.

It is shown that the temperature coefficient of this dehydrocondensation reaction equals γ≈1.5. From the dependence of the reaction rate constants logarithm on reverse temperature, the activation energy of the reaction was calculated, which equals Ea = 32.55 kJ/mol. For copolymers №7* and 9* (Table 16), quantitative values ofMn,Mω,Mz andMω/Mn were determined by gel permeation chromatography methods, which equalMn=1.05-1.62×104 andMω≈1.69-1.98×104; polydispersion degrees, D, of copolymer № 7* and 9* (Table 16) equal ~1.46 and 1.22, respectively.

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Arylenecyclosiloxane oligomers were synthesized in HFC reaction of 1,4bis(dichlororganosilyl)-benzene with dihydroxydiphenylsilane and dihydroxydiphenylsiloxanes in 50–60% anhydrous tolu-ene solution at 1:2 ratio of the initial components both in the presence and in the absence of pyri-dine, which is hydrogen chloride acceptor. The reaction proceeded at room temperature; at the final stage the reaction mixture was heated up to 100°C. The reaction scheme is as follows [87]: R x CI2 Si

R

HO

SiCI2 + 2x HO(SiPh2O)nH

-HCI

Scheme 22

R

R O(SiPh2O)n

Si

Si O(SiPh2O)n

HO

H H

x

Where: R = Me, Ph; n = 1 - 3. After over-precipitation from toluene solution with methyl alcohol, the oligomers synthesized repre-sent solid products with ηspec=0.05-1.0. It is shown that at short length of linear diphenylsiloxane unit, n≤2, oligomers completely soluble in various organic solvents are obtained. The yield of solu-ble part of oligomers is decreased with the length increase, n. Synthesized silarylenecyclosiloxane oligomers and copolymers represent amorphous systems, and the interchain distance in oligomers equals d1=9.98-10.08 Å, approximately. The results of thermo-gravimetric analysis indicate that 5% of the mass is lost at 430-450°C; the main degradation process proceeds in the range of 500-700°C, and in the area of 800°C the mass loss curves become evanes-cent. Further on, dihydroxyarylenecyclosiloxanes were used for synthesizing cyclolinear organosili-con block-copolymers. To clear up action of the origin of organic radicals in organocyclotetrasiloxane fragments on polyad-dition process, as well as to determine contribution of ethylene and phenylene units containing orga-nocyclotetrasiloxane fragments of 1,5- and 1,3-position into cyclolinear copolymers, investigators have studied 1,4-bis(dimethylsilyl)benzene hydride polyaddition to 1,5-divinyl-1,5-dimethyltetra-organocyclotetrasiloxane and 1,3-divinyl-1,3dimethyltetraorganocyclotetrasiloxane in the presence of the catalyst (0.1 M solution of platinum-hydrochloric acid in tetrahydrofuran) [115]. Me n CH2=CH-A-CH=CH2 + n H Si Me

Me H PtCI6 Si H 2 Me

Me Si Me

Me Si-CH2-CH2-A-CH2-CH2 Me

n

Scheme 23

R' R" Me Si H2C=HC Si O Me O O CH=CH2 , Si Si Where: A = O H2C=HC O SiO Me R'R"Si O XV R' R" R’ = R” = Me; R’ = Me, R” = Ph; R’ = R” = Ph.

Me Si CH=CH2 O SiR'R"

XVI

Initial divinylcyclosiloxanes, used in polyaddition reactions, represent a mixture of cisand trans-isomers (at 46:54 ratio). Because these isomers could not be separated by rectification or fractional over-precipitation [115], synthesized silarylene

Organosilicon Oligomers and Copolymers of Bead-Shaped Structure

205

carboorganocyclosiloxanes are considered to be atactic copolymers. Hydrosilylation conditions depend on reactivity of the initial monomers. As 1,4-bis(dimethylsilyl)benzene is quite active hydrosilylating agent, already at 60 70°C it inter-acts with divinylorganocyclotetrasiloxanes containing even four phenyl groups at atoms of silicon; in the case of methyl substituting agents only the reaction proceeds at 50°C. All synthesized copoly-mers are transparent colorless compounds which, in the unique case of methyl substituting agents at atoms of silicon in initial cyclosiloxanes, represent highly viscous-flow polymers; in the case of diphenyl substituting agents, they are transparent solids forming friable soluble films. Table 17 shows physical and chemical parameters of silarylene carboorganocyclosiloxanes. Note that the hig-hest values of [η]=0.42 and 0.48 dl/g are displayed by polymers containing rings with methyl and phenyl groups at single atom of silicon, which are copolymers №1 and 5 (Table 17). In its turn, location of vinyl groups in 1,3- or 1,5-position in OVCS induces clearly determinable regularity. In all considered cases, PFOS viscosity is higher, when two vinyl groups are located in 1,5-position of tetrameric ring. This is apparently associated with disposition of vinyl groups more suitable for hydrosilylation and formation of more symmetrical structure in copolymers №1–3 (structure XV). Table 17. Physical and chemical parameters of silarylene carboorganocyclosiloxanes №

Copolymer structure

R′

1 2 3 4 5

XV XV XV XVI XVI XVI

Me Me Ph Me Me Ph

R″

[η], dl/g

Тdegr* of 5% mass loss, °С

Coke-like residue (800°С), %

Тg,0С

Me Ph Ph Me Ph Ph

0.36 0.48 0.40 0.25 0.42 0.26

450(250) 470(450) 450(350) 325(300) 420(400) 400(375)

50 48 45 57 48 40

-11 +20 +27 -5 +16 +50

In 1H NMR spectra of silarylene carboorganocyclosiloxanes in the area of 5.8 and 4.5 ppm, reflexes from protons belonged to ≡Si-СН=СН2 and ≡Si-Н groups of initial monomers are absent. The reflex at 1.0 ppm, corresponded to protons of -CH2-CH2- group, formed in hydrosilylation reaction. Gene-rally, location of reflexes and the ratio of their intensities in 29 Si and 1H NMR spectra prove the supposed structure of silarylene carboorganocyclosiloxanes. In the case of equimolar ratio of the components, under selected conditions hydrosilylation is almost completed: by NMR and IR-spec-troscopy methods no residual end groups were detected. High-molecular product synthesized posse-sses MM within the range from 1.0×105 to 5.0×105. At the same time, taking into account high volatility of 1,4-bis(dimethylsilyl)benzene compared with divinylcyclotetrasiloxane, the quantity of int-roduced dihydride derivative was increased by 0.1% of the theoretical one, because ≡Si–Н groups are present at the ends of the chain. To eliminate the effect of end groups on physical and chemical parameters, on thermal stability of silarylene carboorganocyclosiloxane, in particular, copolymer so-lution in benzene is treated by the excess of vinylheptamethylcyclotetrasiloxane before over preci-pitation in accordance with the scheme as follows:

206

O. Mukbaniani, G. Zaikov and T.Tatrishvili Me Me Si Me Me Me O O Me H PtCI 2 6 Si H + Si Si Si Me H C=HC O O Me Me Si 2 Me Me Scheme 24

Me Si Me

Me

Me Si

Me Me O O Me Si Si CH-CH2 Si O O Me Me Si Me Me

Variation of the ratio of reagents for hydrosilylation gives an opportunity to obtain both high-mo-lecular products and oligomers with defined chain length, which is very important for synthesis of block-copolymer and polymer networks. After polymer treatment by heptamethylvinylcyclotetrasiloxane, heat resistance of silarylenecarbo-organocyclosiloxanes is slightly increased. The reason is that residual end ≡Si-H groups promoting high-temperature polymer degradation are substituted by higher heat resistant heptamethylcyc-lotetrasiloxane fragments, which causes an increase of thermal stability of the polymer. Estimation of the glass transition temperature of silarylene carboorganocyclosiloxanes and its varia-tion with regard to the origin of substituting agents at atoms of silicon in cyclic rings and introduc-tion of disilphenylene unit into the polymer backbone has indicated that at quite high molecular mass (up to 5.0×105) no high elasticity plateau on thermomechanical curves of the samples is pre-sent. This is probably associated with higher rigidity of silarylene carboorganocyclosiloxanes com-pared with linear poly(organosiloxanes). For the purpose of carbosiloxane network synthesis, at the first stage in accordance with scheme (2.25), silarylene carboorganocyclosiloxanes with 1,4-bis(dimethylsilyl) benzene excess and narrow MMD were obtained [116]. Hence, synthesized oligomers of the structure XV are transparent, colorless and viscous products with MM = 800 - 2,500. At the second stage, polyaddition of reaction (2.23) product with tetramethyltetravinylcyclotetrasiloxane is performed in accordance with the scheme as follows: R' R" Me H Si Me

Me

Me

SiCH2CH2 Si Me

OSiO Me

Me

SiCH2CH2 Si Me OSiO n R' R" Scheme 25

Me

H2PtCI6 Crosslinking Si H [Me(CH =CH)SiO] Croslinking polymer 4 polymer 2 Me

Where: R’ = R” = Me, Ph; R’ ≠ R”. Polymer networks depending on the structure of initial monomers and oligomers are characterized by different framing at atom of silicon and different regulated distance between network points. For the purpose of studying some physical and chemical properties, formation of a network structure directly during film formation from the solution is the unique method of obtaining film samples of polymer networks. Table 18 shows values of strength at break, σb, deformation at break, εb, and elasticity coefficient, E, of studied polymer networks. The data indicate that substitution of methyl groups by phenyl ones and variation of the distance between chain branching centers is accompanied by a significant chan-ge of deformation and strength properties of studied polymers. Note that substitution of both methyl groups by phenyl ones is accompanied by the

Organosilicon Oligomers and Copolymers of Bead-Shaped Structure

207

increase of the elasticity parameter from ~3 to ~600 MPa and the strength from ~1 to ~20 MPa. Besides the possibility of broad variation of mechanical properties, in some cases high mechanical properties may be realized, for example, for a polymer with R' = R" = С6Н5 groups at atoms of silicon (n = 2), which displays high strength (~20 MPa) and elasticity parameter (~600 MPa) combined with quite high deformability (~30%). Table 18. Deformation and strength parameters of films based on silarylene carboorganocyclosiloxanes of the structure XV [117] №

1 2 3 4 5 6 7 8 9

R’

R”

n

σр, MPa

εp, %

E, MP

Me Me Me Me Me Me Ph Ph Ph

Me Me Ph Ph Ph Ph Ph Ph Ph

1 2 1 2 3 4 1 2 3

1,1 0,6 10,8 0,9 0,8 0,6 21,3 19,3 9,5

36 52 158 164 209 234 9 30 50

3,1 1,5 43,0 6,8 0,6 0,3 610 570 350

For the purpose of estimating conformational parameters of silarylene carboorganocyclosiloxanes of the structure XV, two approaches were used [117]: computerized mathematical simulation using the Monte-Carlo method and experimental estimation of the flexibility parameters in solution under natural conditions. In the first case, mathematical simulation has determined the skeletal flexibility of the molecule in the absence of substituting agents at atoms forming the backbone. In the second case, all fragments of the chain, possible interactions with the solvent and temperature effect have been taken into account in the flexibility estimation. For the purpose of experimental estimation of the flexibility parameters in solution, silarylenecarbo-organocyclosiloxanes copolymer 2 (Table 18) with structure XV was fractioned from the benzene (solvent) – ethanol (coagulant) system into 14 fractions. At 25°C in toluene, characteristic viscosity values, [η], of these fractions fall within the range of 5.1 – 0.07 dl/g in toluene. For nine fractions, sufficient quantity of which was obtained, by the light scattering method, values of Мω at the angle of 90° in chloroform (dn/dс ≈ 0.95) on Fika photogoniodiffusometer were measured. For four most high-molecular fractions (Table 19), Мω and (R2)1/2 values at different angles were measured. Polydispersity coefficient of the copolymer was estimated by the GPC method (on KhZh1302 gel chromatograph). For silarylene carboorganocyclosiloxane copolymer 2, GPC data displayМω/Мn =1.34. Table 19 shows values ofМω and (R2)1/2 for silarylene carboorganocyclosiloxane fraction, measured by the light scattering method. As for fractions 4-9Мω values are high, they are measur-ed in non-polarized and polarized light. As these values are close, Table 19 shows the average one for these fractions. Small differences inМω values, measured in polarized and non-polarized light, as well as low scat-tering asymmetry values close for different fractions testify about low polydispersity of the fractions and coil like conformation of macromolecules, which is of

208

O. Mukbaniani, G. Zaikov and T.Tatrishvili

importance for experimental estimation of flexibility parameters by data on [η] and molecular mass of the fractions [117]. Table 19. Values of Мω, scattering asymmetry and the second virial coefficient, A2, for silarylene carboorganocyclosiloxanes fraction [117] № 1 2 3 4 5 6 7 8 9

Мω·10-2

〈R 2〉 z 1/2

206 252 400 883 1072 1381 1866 644.8 12500

298.6 405,7 644.8 1221.4

Scattering asymmetry 1.03 1.06 1.03 1.09 1.05 1.07 1.06 1.20 1.20

А2х10-5, cm2·mol/g2 0.940 0.281 0.221 0.264 0.236 0.202 0.140 0.135 0.093

The dependence of [η] and Мω values in lg[η] – lgМω coordinates, shown in Figure 15, indicates that the following Mark-Kuhn-Hauvink equations are corresponded to silarylene carboorganosilo-xane copolymer: [η] = 0.908·10-3 M0.506 ± 0.049 (toluene, 20°С); [η] = 0.383·10-3 M0.588 ± 0.084 (toluene, 25°С). Values of parameter α in the Mark-Kuhn-Hauvink equation, close to 0.5, which were obtained for silarylenecarboorganosiloxane fractions, allow correspondence of the polymer molecules to the coil- like type and toluene at 20 and 25°C to θ-solvents. As a consequence, extrapolation data of the Mark-Kuhn-Hauvink equation, silarylenecarboorganosiloxane molecules display the coil-like conformation, which is slightly disturbed in toluene at 20 and 25°C by interaction with the solvent.

Figure 15. Dependence of lg[η] on lg Мω for silarylenecarboorganosiloxane in toluene at 25°C (1) and 20°C (2)

Organosilicon Oligomers and Copolymers of Bead-Shaped Structure

209

True value of macromolecule flexibility was calculated from [η], А2 andМω of the fractions using some theoretical equations. Calculation of flexibility parameters at free rotation by the Monte-Carlo method indicates that free rotation of the molecule is possible in four cases only (l2, l4, l5, l6); in three cases it is hindered (l1, l3, l7), which is observed from Table 21 of the schematic presentation of the chain unit (scheme 1). Table 20. Conformational parameters of several organosilicon polymers №

Repeated unit of the Polymer

(〈h2〉 0 /M)x x10 -16

А, Å

Аfr, Å

Sfr= Аfr/l0

S=A/l0

σ

М0/l0 (l0, Å)

Ref.

1

Silarylene carboorganocyclosiloxane

18.91 19.92

19.2

1.04

1.03 1.08

1.02

638/18.4

-

2

~Ме2SiO~

9.4-10

6.0

2

3.2-3.4

1.26

74/2.96

129

3

-CH2CH2SiMe2SiMe2-

0.5461 0.5752 (〈h2〉 fr /M)= 0.555 0.42-0.43 (〈h2〉 fr /M)= 0.24 1.173 0.962

26.5 21.8

5.44

1

4.2 4.8

2.21 2.0

144/6.34

129

5.43 nm2

54

-

-

-

-

198/2.35

116

(〈h2〉 cв /M)= 0.28

-

15

1.3

-

-

618/11.5

112

(CH2)5CH3

4

Si (CH2)5CH3 R R

5

Me

Me

O (SiMe2O)k R R 6

R=Ph, k=1 R=Ph, k=5

0.303

16

10

-

1

1.12

914/21.9

112

7

R=Me, k=0

0.603

233

-

-

4.5

-

283/6.4

58

Note: Calculations have been executed by the following equations: 1 – Curata-Yamakawa; 2 – Stockmayer-Fixman; 3 – Yamakawa-Fudgi.

l1

l2 θ1

CH2 θ2 l3

H 2C

l4 Si

θ4 l 5

θ3

θ6

H 2C l6

Si

l7 θ5

H2C

Si θ7

Scheme 1 In accordance with calculations, current flexibility parameter (〈 h2〉 〈 h2〉

fr

fr/M),

where

is the mean-square distance between macromolecule chain ends at free rotation,

equals 0.555×10-6. If molecular mass of the chain unit equals M0=638 and length of the unit

210

O. Mukbaniani, G. Zaikov and T.Tatrishvili

l0=18.41×10-8 cm, the flexibility para-meter in terms of the Kuhn segment, A, at free rotation equals: Afr = (〈 h2〉

fr/M)Ml

= 19.2 Å.

Specified data show (Table 20) that the Kuhn segment, Afr, and A of silarylenecarboorganosiloxane are comparable with the molecule unitlength (l0 = 18.4 Å). Table 20 shows that for the sequence of silicon-containing high-molecular compounds, this takes place for Afr of poly(ethylenetetramethyl-disilane) (compound 3) and polyorganocyclosiloxane (compound 5), the repeated units of which contain -СН2СН2groups [129] and cyclic fragment, respectively. For the studied silarylene carboorganosiloxane rotation is prohibited both around -СН2СН2- (l3 and l7 bond lengths) and cyclic frag-ments (l1) (Table 21). For estimation of silarylene carboorganosiloxane macromolecules under natural conditions, when the coil is “perturbed” by interaction with the solvent, authors of the work [117] have used the fol-lowing prerequisites observed in the current case: L>>α, i.e. the macromolecule is of the coil-shaped type (α=А/2); low concentrations of solutions, in which the Einstein equation is active; the selected solvent is close to the θ-solvent. Table 21. Bond lengths and unit rotation angles in silarylene carboorganocyclosiloxane chain Bond length, Å

l1=4.25 l2=1.86 l3=1.54 l4=1.87 l5=6.51 l6=1.87 l7=1.54

Angles between bonds (θ ), deg

Type of rotation

54.5 66.0 66.0 68.0 68.0 66.0 66.0

Prohibited (trans) Free Prohibited (trans) Free Free Free Prohibited

For silarylene carboorganocyclosiloxane, (〈 h2〉

-16 0/M)=0.575×10

(Table 20), hence,

the Kuhn seg-ment A equals Kθ=19.9 Å. By the authors [117] it was shown, that (〈 h2〉 value, obtained by [η]/ Μ1/2 extrapolation, coincides with (〈 h2〉

fr/M),

0/M)

which is typical of

Gaussian impermeable coil. On the example of silarylene carboorganocyclosiloxane, the authors of the present work [117] have made an attempt to estimate the value of ML basing on the data on [η] and molecular mass of the studied polymer fraction. Table 21 shows assessment data on conformational parameters, persistent length (α), the Kuhn seg-ment (A) and structural parameter (ML) for silarylene carboorganocyclosiloxane fractions. Average values of α, А and ML, deduced from [η] andМω of silarylene carboorganocyclosiloxane fracti-ons, equal 9.6 Å, 19.2 Å and 34.45×108, respectively. Thus, the structural parameter, ML, calculated fromМω and [η] values, and the one given by chemical structure (ML=34.65×108) of molecules are practically coincident. As a consequence, the above considered Afr really equals 19.2 Å. Under natural conditions, the

Organosilicon Oligomers and Copolymers of Bead-Shaped Structure

211

value of A in solution is close to Аfr; that is why rotation dormancy factor σ = (А/Аfr)1/2=(19.9/19.2)1/2 =1.02. Thus, according to data of mathematical modeling and hydrodynamic studies, obtained by the Shtockmayer-Fixman equation [118], rotation around valence bonds in silarylene carboorganocyc-losiloxane chains is practically free (rotation is possible around l2, l4, l5 and l6 bonds (Table 21). This conclusion was proved by calculations of flexibility parameters of silarylene carboorganocyc-losiloxane molecules, executed by the authors of the present monograph usingМω and A2 values, measured by the light scattering method. The calculations were performed by Krigbaum [119] and Kurata-Yamakava [120] equations. A wide complex of investigations for assessment of conformational parameters of silarylene carbo-organocyclosiloxane macromolecules using hydrodynamic and molecular parameters allowed the authors of the present monograph to make some conclusions. The length of silarylene carborgano- cyclosiloxane macromolecule segment is comparable with the unit length, l0. At free rotation, the Kuhn segment value equals Аfr= 19.2 Ǻ. Under natural conditions, value of the Kuhn segment in so-lution is practically coincident with Afr, and the dormancy parameter of rotation around virtual bond is close to one, i.e. rotation is practically free. This is also proved by the value of characteristic ratio С∞, which is close to one. The chain rotates due to the presence of connective junctions. Thus, as follows from the abovesaid, the “flexibility mechanism” gives silarylene carboorganosiloxane mo-lecules the opportunity to form a dense coil, which approaches the Gaussian impermeable one for high molecular masses and semi-permeable as molecular mass is reduced.

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[36] Makarova N.N., Lavrukhin B.D., Turkeltaub G.N., Kuzmin N.N., Petrova I.M., and Matukhina E.V., Izv. AN SSSR, 1989, No. 6, p. 1351. (Rus) [37] Sommer L.H. and Bennet D.F., J. Am. Chem. Soc., 1959, vol. 81, p. 251. [38] Matukhina E.V., Godovski Yu.K., Makarova N.N., and Petrova I.M., Vysokomol. Soedin., 1995, vol. 37A(10), p. 1680. (Rus) [39] Makarova N.N., Kuzmin N.N., Lavrukhin B.D., Godovski Yu.K., Mamaeva I.I., Matukhina E.V., and Petrova I.M., Vysokomol. Soedin., 1989, vol. 31B(9), p. 708. (Rus) [40] Beatty C.L. and Karasz F.E., Bull. Am. Phys. Soc., 1973, vol. 18(3), p. 461. [41] Godovski Yu.K., Mamaeva I.I., Papkov V.S., and Kuzmin N.N., Macromol. Chem. Rapid Commun., 1985, No. 6, p. 797. [42] Godovski Yu.K. and Papkov V.S., Adv. Polymer Sci., 1989, vol. 88, p. 129. [43] Godovski Yu.K., Makarova N.N., and Kuzmin N.N., Macromol. Chem., Macromol. Symp., 1989, vol. 26, p. 91. [44] Makarova N.N., Kuzmin N.N., Lavrukhin B.D., Godovski Yu.K., Mamaeva I.I., Matukhina E.V., and Petrova I.M., Vysokomol. Soedin., 1989, vol. 31B(9), p. 708. (Rus) [45] Blumshtain A., Polym. J., 1985, vol. 17, p. 277. [46] Wunderlich В. und Orobowicz J., Fortshritte Hochpolym-Forsch., 1984. [47] Makarova N.N., Matukhina E.V., Godovski Yu.K., and Lavrukhin B.D., Vysokomol. Soedin., 1992, vol. 34B(2), p. 56. (Rus) [48] Makarova N.N., Godovski Yu.K., and Lavrukhin B.D., Vysokomol. Soedin., 1995, vol. 37A(3), p. 375. (Rus) [49] Mukbaniani O.V., Achelashvili V.A., Meladze S.M., Koyava N.A., Khananashvili L.M., and Sturua G.I., Soobshch. AN GSSR, 1986, vol. 122(1), p. 105. (Rus) [50] Makarova N.N. and Lavrukhin B.D., Izv. AN SSSR, Ser. Khim., 1986, No. 3, p. 652. (Rus) [51] Makarova N.N., Godovski Yu.K., Matukhina E.V., Volkova L.M., Lavrukhin B.D., and Yakubovich O.V., Vysokomol. Soedin., 1993, vol. 35A(2), p. 136. (Rus). [52] Timofeeva T.V., Boda E.E., Polischuk A.P., Antipin M.Yu., Matukhina E.V., Petrova I.M., Makarova N.N., and Struchkov Yu.T., Mol. Cryst. Liq., Cryst., 1994, vol. 248, p. 125. [53] Makarova N.N., Godovski Yu.K., and Kuzmin N.N. Macromol. Chem., 1987, vol. 188, p. 119. [54] Godovski Yu.K., Makarova N.N., and Mamaeva I.I., Macromol. Chem. Rapid Commun., 1986. vol. 7(7), p. 325. [55] Ebert M., Herrmann-Schoherr O., Wendorff J.H., Ringsdorf R., and Tschirner P., Liq. Cryst., 1990, vol. 7(1), p. 63. [56] Mamaeva I.I., Makarova N.N., Petrova I.M., Tverdokhlebova I.I., and Pavlova S.A., Vysokomol. Soedin., 1987, vol. 29A(7), p. 1507. (Rus) [57] Stockmayer W.H. and Fixman M., J. Polym. Sci., 1963, vol. 1C(1), p. 137. [58] Tsvetkov V.N., Andrianov K.A., Ryumtsev V.I., Shtennikova I.N., Vitovskaya M.G., Makarova N.N., and Kurasheva N.A., Vysokomol. Soedin., 1973, vol. 15A(2), p. 400. (Rus)

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[59] Vitovskaya M.G., Astapenko E.P., Bushin S.V., Skazka V.S., Yamshchikov V.M., Makarova N.N., Andrianov K.A., and Tsvetkov V.N., Vysokomol. Soedin., 1973, vol. 15A(11), p. 2549. (Rus) [60] Tsvetkov V.N. and Andrianov K.A., Eur. Polym. J. 1973, vol. 9, p.27. [61] Tsvetkov V.N., Frisman E.V., and Boitsova N.M., Vysokomol. Soedin., 1960, vol. 2(7), p. 1001. (Rus) [62] Aleksandrova Yu.A., Nikitina T.S., and Pravednikov A.N., Vysokomol. Soedin., 1968, vol. 10A, p. 1078. (Rus) [63] Tomas T.H. and Kendrik T.C., J. Polym. Sci., 1969, vol. 27A, p. 537. [64] Plate N.A. and Shibaev V.P., Comb-Like Polymers and Liquid Crystals, Khimia, Moscow, 1980, p. 303. (Rus) [65] Liquid Crystalline Order in Polymers, Ed. Blumshtein A., Academic Press, New York, 1978. [66] Beatty C.L., Pochan J.M., Froix M.F., and Hinman P.P., Macromolecules, 1975, vol. 8, p. 547. [67] Papkov V.S., Godovski Yu.K., Litvinov V.M., Svistunov V.S., and Zhdanov A.A. International Conference of Socialist Countries on Liquid Crystals, Tbilisi, 1981, vol. 2, p. 201. (Rus) [68] Liquid Crystalline Order in Polymers, Ed. Blumshtein A., Academic Press, New York, 1978, Chapter 9. [69] Pomerantseva M.G., Belyakova Z.V., and Golubtsov S.A., Synthesis of Carbofunctional Organosilanes by Polyaddition Reaction, Moscow, 1971. (Rus) [70] Reikhsfeld V.O., Vinogradova V.N., and Fillipov N.A., Zh. Obshch. Khim., 1973, vol. 43(10), p. 2216. (Rus) [71] Fillipov N.A., Reikhsfeld V.O., Zaslavskaya T.N., and Kuzmina T.A., Zh. Obshch. Khim., 1977, vol. 47(6), p. 1374. (Rus) [72] Andrianov K.A. and Magomedov G.K., Doklady AN SSSR, 1973, vol. 228(5), p. 1094. (Rus) [73] Andrianov K.A., Gavrikova L.A., and Radionov E.F., Vysokomol. Soedin., 1971, vol. 13A(4), p. 937. (Rus) [74] Watanabe H., Kitahara T., Motegi X., and Nagai H., J. Organomet. Chem., 1977, vol. 139(2), p. 215. [75] Souchek I., Andrianov K.A., Khananashvili L.M., and Myasina V.M., Doklady AN SSSR, 1975, vol. 222(1), p. 128. (Rus) [76] Andrianov K.A., Petrashko A.N., Asnovich L.Z., and Gashnikova N.P., Izv. AN SSSR, Ser. Khim., 1967, No. 6, p. 1267. (Rus) [77] Andrianov K.A., Zhdanov A.A., Rodionova E.F., and Vasilenko N.G., Zh. Obshch. Khim., 1975, vol. 45(11), p. 2444. (Rus) [78] Andrianov K.A., Souchek I., and Khananashvili L.M., Uspekhi Khimii, 1979, vol. 48, p. 1233. (Rus) [79] Andrianov K.A., Sidorov V.I., Zaitseva M.G., and Khananashvili L.M., Khim. Geterotsicl. Soed., 1967, No. 1, p. 32. (Rus) [80] Zhdanov A.A. and Astapova T.V., Vysokomol. Soedin., 1981, vol. 23A(3), p. 626. (Rus) [81] Akhrem I.S., Chistovalova N.I., Myisov E.I., and Volpin M.E., Zh. Obshch. Khim., 1972, vol. 42(8), p. 1868. (Rus)

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[106] Damewood I.K. and West I.K., Macromolecules, 1985, vol. 18(2), p. 159. 113. Sundarajian P.R., Macromolecules, 1988, vol. 21(5), p. 1256. [107] Shukla P., Cotts P.M., Miller Ro D., Kussel T.K., Smith B.A., Wallraff G.M., Baier M., and Thiyagarajan P., Macromolecules, 1991, vol. 24(20), p. 5607. [108] Cotts P.M., Ferline S., Dagli G., and Pearson S., Macromolecules, 1991, vol. 24(25), p. 673 [109] Buzin A.I., Sauter E., Godovski Yu.K., Makarova N.N., Rechold W., Vysokomol. Soedin., 1998, vol. 40A(5), p. 782. (Rus) [110] Mukbaniani O.V., Achelashvili V.A., and Sturua G.I., Thes. Rep. XXII All-Union Conf. High-Molecular Compounds, Alma-Ata, 1985, p. 89. (Rus) [111] Mukbaniani O.V., Karchkhadze M.G., Matsaberidze M.G., Achelashvili V.A., Khananashvili L.M., and Kvelashvili N.G., Intern. J. Polym. Mater., 1998, vol. 41, p. 103. [112] Matsaberidze M.G., Candidate’s Dissertation on Chemistry, I. Dzhavakhishvili Tbilisi State University, 2001, Tbilisi, Georgia. (Rus) [113] Nogaideli A.I., Tkeshelashvili R.Sh., Nakaidze L.I., and Mukbaniani O.V., Trudy Tbilisskogo Gos. Universiteta, 1976, vol. 167, p. 69. (Rus) [114] Mukbaniani O., Scherf U., Matsaberidze M., Karchkhadze M., and Khananashvili L., Proce-eding of the Georgian Academy of Science, 1999, vol. 25(1-2), p. 54. [115] Zhdanov A.A., Phyakhina T.A., Afonina R.I., and Kotov V.M., Vysokomol. Soedin., 1993, vol. 35(5), p. 475. (Rus) [116] Zhdanov A.A., Phyakhina T.A., Gritsenko O.T., Kotov V.M., Zhukov V.P., Afonina R.I., and Levin V.Yu., Vysokomol. Soedin., 1992, vol. 33(8), p. 45. (Rus) [117] Tverdokhlebova I.I., Kuznetsov D.V., Pertsova N.V., Kotov V.M., Pryakhina T.A., and Bragi-na T.P., Vysokomol. Soedin., 1993, vol. 35(8), p.1278. (Rus) [118] Stocmayer W.H. and Fixman M., J. Polym. Sci., 1963, No. 1, p. 137. [119] Krigbaum W.R., J. Polym. Sci., 1958, vol. 28(116), p. 213. [120] Kurata M. and Yamakava H., J. Chem. Phys., 1958, vol. 29(1), p. 311.

In: Chemical and Biochemical Physics: New Frontiers ISBN 1-60021-165-8 Editor: G. E. Zaikov, pp. 217-262 © 2006 Nova Science Publishers, Inc.

Chapter 16

ORGANOSILICON COPOLYMERS WITH MONOCYCLIC FRAGMENTS IN THE MAIN DIMETHYLSILOXANE BACKBONE O. Mukbaniani1, G. Zaikov2 and T.Tatrishvili1 1

2

I. Javakhishvili Tbilisi State University, Tbilisi, Georgia Institute of Biochemical Physics, Russian Academy of Sciences, Moscow, Russia

INTRODUCTION It is known [1, 2] that introduction of different components or groups of different chemical origin or structure into the backbone is one of the effective methods for modifying linear organosiloxane olymers. Introduction of alien fragments is resulted in variation of the spiral-shaped structure of dimethylsiloxane polymers, which causes variation of their physical and chemical properties [3]. In particular, introduction of cyclic fragments to linear poly(organosiloxanes) [4, 5] hampers the chain transfer reaction accompanied by ring separation which, in its turn, increases stability of the mentioned polymers. There is some information in the literature about synthesis of polymers with alternating diorgano-siloxane and organosilsesquioxane units [6 – 10] in cyclolinear double-stranded macromolecule of the polymer [11]. The first series of works has used co-hydrolysis products of dimethyldichloro-silane with phenyltrichlorosilane [6, 7], dimethyldichlorosilane with methyltrichlorosilane [8] or methylphenyldichlorosilane with phenyltrichlorosilane [9] for synthesis of the polymers. As a result of anionic polymerization of co-hydrolysis products at equimolar ratio of diorga-osiloxane and organosilsesquioxane units, 3D-polymers were synthesized. Polymerization of bicyc-lodimethylsiloxanes with various lengths of dimethylsiloxane chain between two cyclotetrasiloxane rings has given spatially cross-linked polymers [10]; copolymerization of octamethylcyclotetra-siloxane with polyphenylsilsesquioxane leads to formation of soluble low-molecular polymers [11].

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However, all above-mentioned co-hydrolysis reactions lead to formation of lowmolecular com-pounds with statistical disposition of linear and cyclic fragments, in which statistical disposition of siloxane (D) and silsesquioxane (T) units is preserved. Reviewed in this paper is synthesis of cyclolinear copolymers with regular disposition of mono-cyclic fragments in dimethylsiloxane backbone using HFC and hydride polyaddition reaction as the methods for synthesis of polymers.

1. SILOXANE CYCLOLINEAR COPOLYMERS WITH ORGANOCYCLOTETRA(PENTA, HEXA)-SILOXANE FRAGMENTS IN DIMETHYLSILOXANE BACKBONE HFC reaction of difunctional organocyclosiloxanes with α,ω−dichloro(dihydroxy, dimethylamino)-dimethylsiloxanes of different length (n) proceeding with formation of cyclolinear copolymers pos-sessing regular disposition of cyclic fragments in dimethylsiloxane chain is discussed in the current Section. In HFC reaction study, organocyclotetrasiloxanes with different disposition (1,3- and 1,5positions by edge and diagonal) of functional groups in cyclotetrasiloxane were used [12 – 17]. The effect of substituting agents at silicon atom in difunctional organocyclotetrasiloxanes on reac-tivity of haloid and hydroxyl groups interacting with α,ω−dichloro(dihydroxy)dimethylsiloxanes was studied. Polycondensation of dichlorohexaorganocyclotetrasiloxanes were performed at room temperature in 70% solution of anhydrous toluene or benzene both with acceptor and without it.

Figure 1. Dependence of polycondensation degree between 1,5-dichloro-1,5diorganotetraphenylcyclotetrasilocane and α,ω−dihydroxydimethylsiloxanes: curves 1, 2, 3 – at R = Me, n = 2, 4, 6, respectively; curves 4, 5 – at R = Ph, n = 2, 4, respectively.

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219

When HFC reaction proceeded without acceptor, the run of hydrogen chloride liberation was searched for. Figure 3.1 shows dependence of hydrogen chloride liberation on time at 20°C, whence it follows that as the length of dimethylsiloxane unit increases (n = 2 – 6), conversion by hydrogen chloride decreases from 45% (n = 2, R = Me) to 33% (n = 6, R = Me) (Figure 1, curves 1 – 3). Substitution of methyl side group by phenyl one at silsesquioxane atom of silicon induces abrupt decrease of hydrogen chloride liberation rate from 20 –25% (n = 2, R = Ph) to 5% (n = 4, R = Ph), which is displayed by curves 4 and 5 in Figure 1. Gas-liquid analysis of the product obtained by polycondensation of 1,5dichlorohexaphenylcyclo-tetrasiloxane with 1,3-dihydroxytetramethyldisiloxane has shown that initial compounds are absent in it and octamethylcyclotetrasiloxane, which would be formed by homocondensation of disiloxane-diol in acidic medium is also absent, but products with higher boiling points, i.e. the products of partial intramolecular condensation are present. In the presence of pyridine, HFC reaction of 1,5-dichlorohexaphenylcyclotetrasiloxane with α,ω−dihydroxydimethylsiloxanes proceeds by analogy (at low values of n). Thus basing on data obtained in the study of HFC reaction between dichloro(dihydroxy)organo-cyclotetrasiloxanes with α,ω−dihydroxy(dichloro)dimethylsiloxanes, it has been shown [14] that the reaction is both intermolecular forming cyclolinear copolymer and intramolecular giving bicyclic structures (at low values of n). As a consequence, the current reaction proceeds in accordance with the following scheme: Ph Ph x

Ph Ph R

R

R O (SiMe2O)n H +

R 2xPy + x Y(SiMe2O)n-1SiMe2Y HO . - 2xPy HCI X

X Ph Ph

Ph Ph

x I

Me2Si O O

SiMe2

+ Ph Ph2 II

O

Ph2

Ph

Scheme 1

Where: Х=СI, OH; Y=OH, CI; R=Me, Ph; n=2÷101. Ph

Ph CI + x HO(SiMe2O)nH

x CI Ph Ph

Ph Ph

Ph

2xPy HO - 2xPy .HCI Ph

Ph

Ph O (SiMe2O)n H Ph Ph III

Scheme 2

x

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Where: n = 2÷70. Reactivity of functional groups at their different location in the ring (1,5-or 1,3-position) was estimated in the reaction with α,ω−dihydroxydimethylsiloxane with the polymerization level n = 25, 70 at 180°C in block. From experimental data a conclusion was made [18] that 1,3- and 1,5-po-sitions of chlorine atoms at silicon in dichlorohexaphenylcyclotetrasiloxane interacting with α,ω− dihydroxydimethylsiloxanes cause a negligible effect on their reactivity during polycondensation (Figure 2), which runs counter to the conclusion in the ref [19]. At room temperature, polycondensation of 1,5-dihydroxyhexaphenylcyclotetrasiloxane with α,ω− dichlorodimethylsiloxanes in 70% solution of anhydrous toluene proceeds at deeper level, and con-version by hydrogen chloride reaches 60%, whereas in HFC reaction of 1,5-dichlorohexaphenyl-cyclotetrasiloxane with α,ω−dichlorodimethylsiloxanes it is below 30% (Figure 3).

Figure 2. Dependence of hydrogen chloride liberation rate in polycondensation reaction of dichlorohexaphenylcyclotetrasiloxane with α,ω−dihydroxydimethylsiloxanes: curves 1 and 2 – with 1,5disposition of chlorine atoms and at n = 25,70, respectively; curves 1 and 2 - with 1,3-disposition of chlorine atoms and at n = 25,70, respectively.

Figure 3. Hydrogen chloride conversion in polycondensation of 1,5-dichloro-and 1,5dihydroxyhexaphenylcyclotetrasiloxanes with α,ω−dihydroxy(dichloro)-dimethylsiloxanes (n = 2, 4): curves 1 and 2 -for 1,5-dichlorohexaphenylcyclotetrasiloxane with n = 4, 2 respectively; curves 3 and 4 – for 1,5dihydroxyhexaphe-nylcyclotetrasiloxane with n = 4, 2 respectively.

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As the screening effect of substituting agents at silicon atoms is considered separately, they display equal values of it. Thus, for estimating reactivity of functional groups in current reactions [18], both the screening effect of substituting agents at silicon atoms linked to reactive groups and the inductive action of this radical on the reactive group are considered. Because maximal conversion by hydrogen chloride did not exceed 50 – 60%, the acceptor (pyridine) was introduced for the purpose of increasing the depth of HFC proceeding. It is shown that under experimental conditions at 23 – 25°C condensation of α,ω−dihydroxydime-thylsiloxanes by hydroxyl groups does not proceed, which correlates with the previous conclusions [20]. In this work it is indicated that homofunctional condensation of 1,3-dihydroxytetrame-thyldisiloxane does not proceed even in the presence of more basic amines. As HFC proceeds in 60 – 70% solution of anhydrous toluene in the presence of pyridine, the yield of copolymers is increased to 72 – 93%, and copolymers synthesized after reprecipitation represent colorless or light-yellow transparent solids of viscous substances, well soluble in usual organic solvents with ηspec = 0.1 - 0.5. Study of the reaction (1) has indicated that at short length of linear dimethylsiloxane unit the yield of copolymers after reprecipitation is much lower. After eliminating solvent from the mother solution, a viscous product with molecular mass of ~830 units was obtained. Such molecular mass can be displayed by the product of intramolecular condensation with the structure II only. To prove the possibility of forming compound with the structure II, direct synthesis of this compound was performed [21]. Results of the current synthesis were also used for estimation of cis- and trans-isomers’ contents in the initial 1,5dichlorohexaphenylcyclotetrasiloxane. Namely, HFC reaction of a mixture of cis- and transisomers of 1,5-dichlorohexaphenylcyclotetrasiloxane with 1,3-dihydroxytetramethyldisiloxane was studied (equimolar ratio of initial reagents, 5% anhydrous toluene so-lution, 0°C, in the presence of acceptor – pyridine). In the case of cis-isomer, formation of poly-cyclic structured compound is the most probable, whereas trans-isomers give polymeric products. The reaction proceeds in accordance with the scheme as follows:

Ph Ph R CI Ph Ph

2Py R + HO(SiMe2O)2H -2Py.HCI CI

O Ph2

Ph II

Ph

Ph

Ph2

Me2 Si O O SiMe2

Ph Ph2

+

O Me2 Si O Me2Si O Ph

O Ph2 SiMe2 O SiMe2 O

Ph2

Ph

IV

Ph2

Scheme 3

Composition and structure of the individual polycyclic compounds, synthesized by fractionation in high vacuum, were determined on the basis of the ultimate analysis by determination of the molecular mass, IR and 1H NMR spectral data. Based on this reaction, the authors have concluded that 1,5-dichlorohexaphenylcyclotetrasiloxane used in HFC reactions represents a mixture of cis- and trans-isomers. The cis-form promotes for structures

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II and IV formation, total yield of which equals ~50%; the rest 50% are represented by oligomeric structures, formed from trans-forms of 1,5-dichlorohexaphenylcyclotetrasiloxane. Spectral data of 1H NMR analysis have indicated the regular structure of cyclolinear copolymers, which correlates well with the data from the literature [22]. Some physical and chemical parameters of copolymers with cyclotetrasiloxane fragments in the backbone are shown in Tables 1 – 2. Table 1. Some physical and chemical parameters and yield of structure I cyclolinear copolymers with 1,5-disposition of cyclotetrasiloxane fragment in dimethylsiloxane backbone

x

HO

R

Ph2

Ph2

R

(SiMe2O)n H

№ Copolymer R nSiO Yield, % Тg,0С ηspec* 1 Me 2 72 -54 0.15-0.16 2 Me 4 83 -57 0.09-0.16 3** Me 5 86 0.20 4 Me 6 86 -71 0.10-0.22 5 Me 12 90 -94 0.24-0.27 6** Me 25 90 -117 - 0.33 7 Me 51 91 -123 - 0.40 8 Me 70 93 -123 0.42 O 9 Me 101 96 -123 - 0.49 10 Ph 2 72 0.06-0.11 -10÷-20 11 Ph 4 80 -34 0.10-0.14 12 Ph 6 93 -55 0.10-0.21 13 Ph 12 93 -83 0.19-0.26 14 Ph 25 95 -110 0.19-0.34 15 Ph 51 96 -123 - 0.40 16 Ph 70 92 -123 0.15 Ph 101 97 -123 - 0.42 17 * Hereinafter, second values of viscosity are obtained by high-temperature polycondensation of 1,5dihydroxyorganocyclohexasiloxanes with α,ω−bis(dimethylamino)dimethylsiloxanes. ** For these samples, viscosities in benzene are determined.

Table 2. Some physical-chemical parameters and yield of cyclolinear copolymers of the structure III № 1 2 3 4 5 6

Copolymer

Ph

Ph O (SiMe2O)n H

HO Ph Ph

Ph Ph

x

nSiO 2 4 6 12 25 70

Yield, % 83 90 91 92 93 92

Тg,0С -23 -35 -83 -107 -123

ηspec 0.06 0.10 0.11 0.31 0.37 0.49

For copolymers, thermomechanical studies were carried out in accordance with the technique, described in ref. [23]. Expectedly, based on the data from the literature [24, 25] the studies have shown that the presence of inclusions of any chemical origin in the polydimethylsiloxane backbone (framing groups different from methyl ones, rings of

Organosilicon Copolymers with Monocyclic Fragments …

223

different structure, branching points) causes the loss of the ability of copolymers to crystallize, if the distance between neighboring inclusions equals ~30 siloxane units. Copolymers with n = 2 – 25 studied do not crystallize, and the ones with n = 70 behave as crystallizing poly(dimethylsiloxanes) (PDMS). The temperature range corresponded to glass tran-sition in copolymers regularly expands towards higher temperatures with decrease of n. Of special attention is the fact that disposition of cyclotetrasiloxane fragment in the poly(dimethylsiloxane) backbone (1,5- and 1,3-positions) causes a negligible effect on Tg of the copolymers (Figure 4).

Figure 4. Thermomechanical curves for copolymers with 1,3- and 1,5- disposition of cyclotetrasiloxane fragments in PDMS backbone: 1, 2, 3, 4, 5 for copolymers with 1,3-disposition of hexaphenylcyclotetrasiloxane fragment in the backbone at n = 2, 4, 12, 25, 70 respectively; 1I, 2I, 3I, 4I - for copolymers with 1,5-disposition of hexaphenylcyclotetrasiloxane fragment in the backbone at n = 2, 4, 12, 25, respectively (100 g load, 5 deg/min heating rate).

Of special importance is the fact that introduction of rings containing phenyl framing groups into the linear chain is accompanied by Tg increase, compared with cyclolinear carbosiloxane polymers containing methyl framing groups [26]. In the case of cyclotetrasiloxanes with phenyl groups, Tg increase is higher than under the action of network points, which do not change Tg of PDMS networks at n = 20 [27]. The latter is determined by a significant effect of bulky phenyl groups, the presence of which at any place of PDMS backbone significantly increases Tg [28]. Substitution of phenyl side group by the methyl one in organosilsesquioxane fragment of organocyclotetrasiloxanes decreases the glass tran-sition temperature by ~15 - 20°C. The effect of cyclotetrasiloxane fragment is detected at dime-thylsiloxane unit n = 25 long and lies above Tg of PDMS. Thermogravimetric studies of cyclolinear copolymers indicate that 1,3-and 1,5dispositions of hexa-phenylcyclotetrasiloxane fragment cause no difference in mass losses of copolymers. As a result, by HFC reaction of 1,5-dihydroxy-1,5-bistrimethylsiloxytetraphenylcyclotetrasiloxane with α,ω−dichloromethylsiloxanes in the presence of pyridine and in 60% anhydrous toluene so-lution at 20 - 25°C cyclolinear copolymers with regular disposition of 1,5-bistrimethylsiloxy-tetraphenylcyclotetrasiloxane in the dimethylsiloxane backbone, completely dissoluble in organic solvents, were synthesized [29]. The reaction proceeds in accordance with the general scheme as follows:

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O. Mukbaniani, G. Zaikov and T.Tatrishvili

x

HO

Ph2

Me3SiO Ph2

Ph2 OH

2xPy + x CI(SiMe2O)n-1SiMe2CI

-2xPyHCI

OSiMe3

O (SiMe2O)n H

HO OSiMe3

Me3SiO Ph2

x I

Scheme 4

Where: m = 1, 2, 3, 10. Depending on the length of dimethylsiloxane unit, copolymers represent crystalline (Tg=100°C, n= 1), rubbery (Tg =30°C, εelong=400%) and quite strong (δbreak=40 kg/cm2 at 24°C) products. Of interest is that dielectric constant of this polymer decreases linearly with the temperature increase. A suitable method has been suggested [12] for obtaining cyclolinear copolymers, which concludes in high-temperature HFC reaction of dihydroxyorganocyclotetra(penta, hexa)siloxanes with α,ω− bisdiamino(dimethylamino)dimethylsiloxanes. The method suggested is simpler than the above-dis-cussed reactions (1) and (3), because synthesized copolymers possess low molecular mass. More-over, obtaining of pure copolymers in accordance with the above-shown schemes (1) and (2) requ-ires application of an additional stage of polymer purification from secondary product which is ami-ne hydrochloride. For the purpose of synthesizing cyclolinear copolymers with regular disposition of organocyclotetra- organocyclopenta- and organocyclohexasiloxane fragments in linear the dimethylsiloxane backbone, HFC reaction of 1,5-dihydroxy-1,5dimethyl(diphenyl)phenylcyclotetra(penta, hexa)siloxanes and 1,7-dihydroxy-1,7dimethyl(diphenyl)octaphenylcyclohexasiloxane with α,ω−bis(dimethylamino)(dichloro)dimethylsiloxanes was studied [15 – 17]. In this case, the reaction proceeds in accordance with the general scheme as follows: R x

Z

O(SiPh2O)m Si

Si O(SiPh2O)l

R + x Y(SiMe2O)n-1 SiMe2Y

Z

R

O(SiPh2O) m R Si (SiMe2O)n

Si O(SiPh2O) l

x

Scheme 5

Where: Z = OH, CI; Y = Me2N, OH; R = Me, Ph; m = l = 1 - structure I; m = 1, l = 2 structure V; m = 1, l = 3 - structure VI; m = l = 2 - structure VII. HFC was studied at 20-150°C in anhydrous nitrogen or argon flow both in block and in solution. As the reaction proceeds in block, the reaction mixture is heated up to 50-60°C until a homogeneous mixture is formed; thereafter, the reaction is continued in vacuum at P =3–5 mmHg and temperature range of 120-150°C up to constant viscosity. Application of reactive α,ω−bis(dimethylamino)dime-thylsiloxanes allowed performance of the initial stage of the reaction in solution at 20-50°C until a homogeneous mixture is formed. For more complete elimination of amine, liberated in the reaction, the mixture is aerated by dry inert gas. Polymers synthesized by this technique require no purifica-tion, because amines obtained as secondary reaction products possess very low boiling point and are completely removed from

Organosilicon Copolymers with Monocyclic Fragments …

225

the reaction mixture. In as much as the mixture of dichloro(dihydroxy)-organocyclosiloxanes isomers was used in HFC, atactic copolymers were synthesized. In the case of HFC of 1,5-dihydroxyhexaphenylcyclotetrasiloxane with α,ω−bis(diethylamino)di-methylsiloxanes, gel formation proceeds after diethylamine conversion reaching ~5%. Previously, it was informed about a possibility of siloxane bond break in trimethyltriphenylcyclotrisiloxane by diethylamine and formation of a complex with the charge transfer [30]. In accordance with the authors’ opinion [15–17], immediate removal of diethylamine produced in the reaction with α,ω−bis(diethylamino)dimethylsiloxanes could be hardly guaranteed. In its turn, dimethylamine interacts with the siloxane bond in the cyclic fragment and forms bipolar zwitter-ions [31]. The HFC reaction proceeding with α,ω−bis(diethylamino)(diamino)dimethylsiloxanes [12] forms copolymers completely dissoluble in organic solvents, because dimethylamine and ammonium liberated during synthesis cause no breakage of siloxane bonds in cyclic fragments of the polymeric backbone. It is proved that at short lengths of dimethylsiloxane unit, HFC reaction proceeds in two directions: intramolecular ring formation giving polycyclic products and intermolecular formation of cyclo-linear copolymers. Formation of polycyclic products is proved by the direct synthesis. To prove formation of copolymers with regular disposition of cyclic fragments in macromolecular backbone, some copolymers were fractionated into several fractions. Results of the ultimate analysis have indicated that the values detected for fractions coincide with the calculated ones, which rep-resents direct proof of the regular structure of copolymers. Many investigators have studied dissolved solutions of poly(organosiloxanes) with different side groups at silicon atoms in the macromolecule backbones [32 - 35]. These works show results of the studies of the effect of the side groups origin, their disposition and the influence of hydrodynamic and conformation parameters of macromolecules. Table 3. Bond lengths and angles between them in poly(organocyclosiloxanes) of the structure I (n = 1) Bond l1 l2 l3 l4 l5 *

Bond length, Å 4.25 1.63 1.63 1.63 1.63

θI*, deg 54.5 37.0 70.0 37.0 54.5

Rotation conditions Prohibited Free Free Free Free

For the polymer backbone, this coefficient is exclusively associated with the structure of macromolecules and potentials of internal rotation around internal bonds of the backbone. This dependence gives information about energy of the chain conformation and mutual transitions.

The effect of introduction of regularly disposed cyclic fragments into the macromolecular backbone on conformational and hydrodynamic parameters is also studied [30]. For this purpose, copolymers 3 and 4 (Table 1) were fractionated into twelve fractions from the benzene (solvent) – methanol (precipitator) system. The influence of cyclic groups, introduced into the polymer backbone, on rigi-dity parameters was determined by direct computer simulation of macromolecular coil with the help of the Monte-Carlo method.

226

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The process was simulated for the copolymer of the structure I with n = 1, 5 and 10 in the structural unit of dimethylsiloxane chain, and the Kuhn segment A and /nM0 were calculated, where M0 is the molecular mass of the structural unit, is the mean-square distance between chain ends at free rotation around virtual bonds1, n is the number of structural units. Structural unit of the copolymer was simulated on the basis of the data from the literature on the simplest molecules’ structure, close by the composition and structure to monomeric units. Shown below is the geometrical structure of repeated structural unit in poly(organosiloxane) at n=1. Table 3 shows values of bond lengths and angles between them. 1 By the term of virtual bond the area of the chain is meant, rotation around which is possible. In particular case, it may be a simple valence bond –(l2-l5); in the general case, it may contain not only valence bonds, but also rings, or may determine the distance between atoms in the ring as (l1) does.

Si

Si O l O 1

Si

l2 O Q 2 l3 Q1

l4 O Q 4 l5 Si Si Q3

O Q5

O

O Si

To avoid the ring twisting, rotation around virtual Si-------Si (l1) bond is prohibited. Table 4 shows calculation results, which represent theoretical values of the Kuhn segment (A) and /nM0 for polymers of the structure I (n=1; n=5; n=10) and, for comparison, analogous values for PDMS [37]. Table 4. Calculation values of the Kuhn segment (A) and /nM0 Polymer of structure I

Me

Ph2

HO Ph2 PDMS

Me O (SiMe2O)n H

nSiO

A=/nl0A

/nM0

1 5 10

15 10 10

0.28 0.24 0.22

10

10

0.24

x

These theoretical data show that the influence of the octatomic siloxane ring is observed at n=1 only. Saturation is observed already at transition from n=5 to n=10, and increase of the quantity of ≡SiO- groups causes no effect on the coil size. For the fraction of copolymer 3 of the structure I and n = 5, experimental values of the Kuhn segment and /nM0 are shown in Table 4. One of the methods for estimating experimental thermodynamic flexibility of the polymer backbone is determination of parameters, associated with the size of isolated

Organosilicon Copolymers with Monocyclic Fragments …

227

macromolecule coil. At the pre-sent time, methods of macromolecular coil parameter estimation under ideal and non-ideal conditi- tions. In the first case, characteristic viscosity of the fraction, [η], with the known molecular mass in ideal θ-solvent was measured. This method is based on the known Flory-Fox relation [38]. The second method represents measurements of the fraction [η] in good thermodynamic solvents and extrapo-lation of experimental data in accordance with the known techniques [39 - 41]. Because in the cur-rent work [36] all measurements were performed in good thermodynamic solvent, unperturbed di-mensions of macromolecules, , were determined by graphical extrapolation in accordance with the Shtockmayer-Fixman, suggested by the authors for flexible macromolecules, in [η] М1/2-М1/2 coordinates (Figure 6).

Figure 6. Determination of unperturbed dimensions by extrapolation in accordance with the ShtockmayerFixman method for copolymers 3 (Table 1): 1 – at 25°C; 2 - 40°C; 3 - 50°C.

Table 5 shows mean-weight molecular masses,Мω, and [η] for the fraction of copolymer 3 (n = 5) (Table 1) of the structure I at 25, 40 and 50°C in toluene. Table 5. Molecular masses and characteristic viscosities of copolymer 3 fractions (Table 1, structure I) at different temperatures Fraction №

1 2 3 4 5 6 7 8 9 10 11 12

Μωх10-3

9.0 17.0 22.0 26.0 33.0 42.0 44.0 72.0 85.0 92.0 141.0 239.0

[η] in toluene (dl/g) at temperature, °C 25 40 50

0.04 0.06 0.07 0.08 0.09 0.12 0.11 0.15 0.16 0.19 0.26 0.33

0.07 0.09 0.10 0.11 0.13 0.13 0.15 0.17 0.20 0.23 0.38

0.13 0.11 0.15 0.12 0.14 0.15 0.12 0.18 0.21 0.38 -

228

O. Mukbaniani, G. Zaikov and T.Tatrishvili Table 6. Experimental conformational parameters of copolymer 3 (structure I, Table 1) № 1 2 3

Т, 0С 25 40 50

Kθх103 0.46 0.58 0.67

/nM0 0.303 0.340 0.380

А, Å 16.0 18.0 20.0

σ=(/)1/2 1.12 1.18 1.25

Table 6 shows experimental values of conformational parameters for the Kuhn segment, А= /nl0 (where l0 is the structural unit length), hindrance factor of rotation around the single bond, σ=(/)1/2, and constants of the Mark-Kuhn-Hauvink equation, Kθ≈[η]/Μ1/2, at different temperatures. Experimental data on conformational parameters of copolymer 3 (Table 1), shown in Table 6, exce-ed these calculated in the supposition that rotation around virtual and valence bonds is free. Comparison of experimental and calculated values of the abovementioned parameters indicates the hindrance of rotation around valence bonds ≡Si-O- and ≡Si-Ph, due to their short lengths, because distances between neighboring atoms Si----Si and О----О are shorter or close to the sum of Vander-Waals radii of these atoms. Data from Table 6 indicate also that experimental values of the hind-rance factors are low. As shown by Flory, these low values of σ, i.e. a negligible increase of PDMS molecule dimension compared with dimensions, calculated in the supposition of free rotation, are associated with pre-dominant containing of the plane trans-chain type conformation rather than the absence of rotation hindrance, compared with coiled conformations. Hence, low у values for these chains may be realiz-ed at both low and high differences of energies of rotational isomers under the condition of energy gain of the trans-shape [42,43]. On the other hand, low у must be combined with positive teperatu-re coefficient of unperturbed dimensions of macromolecules2, because relative content of the trans-shape must decrease with temperature growth [42, 43]. For linear PDMS, studies of the temperature coefficient of unperturbed dimensions of macromolecules were carried out in the work [44], and the value obtained equaled (0.78 ± 0.06) х10-3deg-1. For the purpose of determination of the temperature coefficient for unperturbed dimensions of copolymer 3 (Table 1), [η] values were measured in the same solvent (toluene) at different tempe-ratures. In accordance with the Shtockmayer-Fixman method, Kθ=(/M)1/2xF0 values was deter-mined using the least-square technique. The temperature coefficient of unperturbed dimensions was calculated from the values obtained at different temperatures (Table 6) using the relation, suggested in the work [45]: dln/dT = 2/3xlnKθ/dT. The coefficient of unperturbed coil dimension (dln/dT), determined for copolymer 3 (Table 1), equals 0.85x10-3 deg-1 [44]. Thus, data shown in Table 6 indicate that thermodynamic rigidity, mean-square dimensions and hindrance of copolymer 3 chains (Table 1) are increased with temperature. These facts as well as positive temperature coefficient of unperturbed dimensions testify about predominance of coiled trans-shape, more energetically preferable for copolymer 3 chains, similar to PDMS, compared with isomers. As temperature increases, the fracture of plane trans-chains decreases, which, as a result of 2For polymeric chain, this coefficient is

Organosilicon Copolymers with Monocyclic Fragments …

229

associated with the structure of macromolecules and potentials of internal rotation around internal bonds in the backbone. Such dependence gives infor-mation about energetic conformation of the backbone at mutual transitions. transition from trans- to gauche-state, proceeds with an increase of unperturbed dimensions [41]. Summing up all above-discussed, one may conclude that, compared with PDMS, introduction of octatomic cyclic fragments with symmetrically disposed phenyl side groups causes no change of internal rotation conditions, as it takes place for poly(methylphenylsiloxane) with asymmetrical side phenyl groups [43]. However, already for 1:5 ratio (1 cyclic group per 5 siloxane units), i.e. at the decrease of the distance between cyclic fragments in the backbone, their introduction into dimethyl-siloxane backbone induces a significant increase of thermodynamic rigidity of macromolecules. The rigidity increase of copolymer 3 is also displayed in thermomechanical properties of copolymers. For example, Tg of copolymer 3 (Тg = -50°С) is much higher than Tg of PDMS. The study of hydrodynamic behavior of copolymer 6 (Table 1) indicates that, apparently, macromo-lecules of this copolymer possess branched backbones. In the Mark-Kuhn-Hauvink equation, parameter α for copolymer 6 solution in toluene at 25°C equ-als 0.30, which is typical of branched macromolecules. For cyclolinear polymer 3 under the same conditions, this parameter equals 0.62 (Figure 7). Molecular masses vary within the range from 4x103 to 565x103.

Figure 7. Dependence of lg[η] on lg М: 1 – for copolymer 3 in toluene at 25°С, [η]=1.394x10-4М0.62; 2 – for copolymer 6 at 25°С, [η]=1.79x10-2М0.30; 3 – for copolymer 6 in isopropyl alcohol at 22°С, [η]=9.86x104 0.53 М .

Mean-weight molecular masses,Мω, were measured on Sofica device. Moreover, molecular masses below 104 were also determined by the ebullioscopy method (Мn). Good coincidence betweenМω andМn was obtained. The reason for branching may be the fact that initial oligomers α,ω−dichlo-rodimethylsiloxanes) for synthesizing cyclolinear copolymers [poly(organocyclotetrasiloxanes)] with n=5 and 10 were produced by partial hydrolysis reaction of dimethyldichlorosilane, and oligo-mers with n=25 were telomerized in autoclave [46], which may cause formation of copolymers containing units capable of branching. Additional proof of branching is the loss of copolymer 6 so-lubility with time. However, behavior of copolymer 6 under θ-conditions, different from the beha-vior of

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O. Mukbaniani, G. Zaikov and T.Tatrishvili

branched macromolecules was observed. Parameter α equaled 0.53, which exceeded α=0.25 typical of branched copolymers under θ-conditions. For copolymer 6, θ-conditions was set on a de-vice of temperature polymer precipitation. Isopropyl alcohol at 22°C was used as θsolvent (Figure 8). The attempt to prove correctness of θ-conditions selection for copolymer 6 by checking equality to zero of the virial coefficient, A2, has given interesting results. It has been found that purification of the polymer solution from dust by filtration via dense Shott filter (№ 5) causes a sharp increase of light scattering intensity, which does not allow measurement of molecular mass and A2. Repeated filtering induces much more sharp increase of light scattering intensity. The precipitation temperature of filtered solution is increased. This fact contradicts to the supposition that copolymer 6 represents a branched structure. Possible reason for this effect may be solution structuring during long-term filtration. To check this suggesting [36], copolymer solutions (filtered and non-filtered) were studied on optical microscope. Films obtained from 1% filtered solution displayed oriented chains and aggregates from them, which were not observed in the films from non-filtered solution. Studies carried out with the help of electron microscope have not allowed definite conclusions, because the technique requires dilution to 0.01-g/ml concentration of the solution, i.e. an order of magnitude lower than that, at which molecular mass is determined.

Figure 8. Dependence of critical precipitation temperature, T0cr, of copolymer 6 fractions (Table 1) on molecular mass.

Thermogravimetric studies of copolymers 2 and 4 (Table 1) have determined the influence of regu-larly disposed organocyclotetrasiloxane fragments in linear dimethylsiloxane chain on thermal sta-bility of the studied copolymers. Pyrolytic spectrum (Figure 9) indicates that thermal degradation of polymers 2 and 4 below 300 and 350°C, respectively, displays full absence of organosilicon and organic compounds in the pyrolysis products. At 350 - 400°C, thermal degradation rate is considerably increased, and the reaction proceeds with benzene isolation. In 380 - 440°C temperature range, degradation products display cyclosiloxane components of Dn composition, D4<1.5%. Note also that pyrolysis temperature increase induces sharp increase of CH4, D3 and D4 compounds extracted. Liberation of benzene and methane is due to ≡Si-C and C-H bond break, which induces crosslinking at the expense of methyl and phenyl groups [47].

Organosilicon Copolymers with Monocyclic Fragments …

231

Figure 9. СН4, С6Н6, D3 and D4 liberation curves for cyclolinear copolymers 2 and 4 (structure I, Table 3.1).•-С6Н6, ○-СН4, х- D3 and D 4 (<1.5%). Here - is corresponded to copolymer 2 and ---- to copolymer 4.

It has been shown before [47–51] that degradation proceeds by the radical mechanism, mainly forming oligomeric products instead of organocyclosiloxanes. Such phenomenon was observed in studies of thermal degradation of organocyclosiloxane cyclolinear copolymers [49]. This gives an opportunity to suggest that thermal pyrolysis of copolymers 2 and 4 is guided by the backbone break in compliance with the law of randomness with formation of oligomeric products. Simultaneously with the backbone degradation, radical cross-linking reactions by methyl and phenyl groups pro-ceed, accompanied by hydrogen, methane and benzene liberation. Introduction of organosiloxane cyclic fragments into linear dimethylsiloxane backbone induces a considerable decrease of the deg-radation process of such copolymers by depolymerization mechanism at 320 - 340°C, whereas un-blocked PDMS is polymerized by almost 95% at these temperatures. The general feature of all co-polymers is decrease of their thermal oxidative stability and increase of final mass losses with dimethylsiloxane unit length increase. Comparative estimation of thermal oxidative stability of copo-lymer proves negligible effect of 1,5- or 1,7-disposition of cyclohexasiloxane fragments (similar to organcyclotetra-siloxane fragments) on thermal oxidative stability of copolymers. Furthermore, at the increase of cyclic fragment volume, i.e. at transition from organocyclotetra-siloxane fragment to organocyclopenta- and organocyclohexasiloxane ones, at the same length of di-methylsiloxane unit induces a decrease of thermal oxidative stability of the copolymers, which, in turn, is explained by increase of the mass part of phenyl groups. Comparative thermomechanical studies of copolymer with organocyclotetra-, organocyclopenta- and organocyclohexasiloxane (1,5- and 1,7-positions) fragments in the chain have been implemen-ted. Data on Tg of copolymer, shown in Table 7, indicate that the increase of dimethylsiloxane unit length leads to obligate decrease of Tg of the copolymers. It has been found that both cases of hexa-phenylcyclotetrasiloxanes (1,3- and 1,5-positions) and organocyclohexasiloxanes 1,5- or 1,7-dispo-sition of cyclic fragments with the same framing groups at atom of silicon in silsesquioxane and equal length of the linear dimethylsiloxane unit causes negligible effect on Tg of copolymers.

232

O. Mukbaniani, G. Zaikov and T.Tatrishvili Table 7. Some physical and chemical parameters of copolymers with organocyclopentasiloxane (structure V) fragments in the main backbone №

1 2 3 4 5 6 7 8 9 10 11 12 13 14

Copolymer

R

Ph2 R

O (SiMe2O)n H

HO Ph2

x

Ph2

R

nSiO

Ме Ме Ме Ме Ме Ме Ме Ph Ph Ph Ph Ph Ph Ph

2 4 6 8 12 40 51 2 4 6 8 12 40 51

Yield, % 77 81 93 96 96 94 97 79 83 93 93 93 96 98

ηspec

Тg,0С

0.08 0.13 0.14 0.18 0.20 0.25 0.32 0.06 0.08 0.11 0.14 0.18 0.23 0.29

+15 -14 -38 -65 -123 -123 +15 0 -25 -50 -123 -123

Table 8. Some physical-chemical parameters of copolymers with the structure VI № 1 2 3 4 5 6 7 8 9 10

Copolymer

R

Ph2

HO

R O (SiMe2O)n H Ph2

Ph2 Ph2

x

R

nSiO

Me Me Me Me Me Ph Ph Ph Ph Ph

2 4 8 34 51 2 4 8 34 51

Yield, % 75 80 83 88 90 76 81 82 87 91

η spec

Тg,0С

0.09 0.14 0.17 0.26 0.30 0.10 0.13 0.18 0.24 0.29

+10 -1 -47 -123 -123 +21 +8 -38 -123 -123

From Tg dependence on dimethylsiloxane unit length, indicates that the increase of Tg of copolymers with the number of phenyl groups and volume of cyclic fragment. Partial substitution of methyl groups at silicon atom in silsesquioxane fragment by phenyl ones will increase Tg by ~10°C. Similar dependence was detected for all copolymers with cyclic fragments in dimethylsiloxane backbone. X-ray diffraction studies were carried out for cyclolinear copolymers and it was shown, that they are amorphous systems. Independently of the length of single-unit dimethylsiloxane chain, diffraction patterns display two amorphous halos. It is known that the first amorphous halo, d1, characterizes the average interchain distance in amorphous polymer [52], whereas d2 is more complicated and corresponds to both intrachain and interchain or interatomic distances.

Organosilicon Copolymers with Monocyclic Fragments …

233

Table 9. Some physical-chemical parameters of copolymers with the structure VII № 1 2 3 4 5 6 7 8 9 10 11 12

Copolymer

R

Ph2 Ph2

HO

R O (SiMe2O)n H

Ph2 Ph2

x

R

nSiO

Me Me Me Me Me Me Ph Ph Ph Ph Ph Ph

2 4 6 12 51 101 2 4 6 12 51 101

Yield, % 85 92 93 94 94 96 82 90 93 93 94 96

ηspe c 0.06 0.08 0.17 0.21 0.26 0.37 0.05 0.07 0.13 0.19 0.22 0.35

Тg,0 С +11 0 -50 -123 -123 +24 +14 -35 -54 -123 -123

For copolymers with cyclopentasiloxane and cyclohexasiloxane fragments in dimethylsiloxane backbone, difference in d1 values is negligible. Maximal interchain distance (d1 = 9.60 - 9.54 Å) is observed at short lengths of dimethylsiloxane chain (n = 2, 4), and d1 is decreased to 7.20 Å, i.e. to PDMS interchain distance, with increase of the length, n. It is known from the literature that occurrence of the mesomorphous state in cyclolinear siloxane polymers (CLSP) is mainly determined by the size of cyclosiloxane fragment, i.e. by the number of diorganosiloxane groups in the structure of cyclosiloxane fragment, and its symmetrical disposition in the polymeric backbone [53], molecular mass [54] and tacticity of the polymer backbone [55]. Mesomorphous state of CLSP occurs at sufficient length of symmetrical alkyl substituting agents (R = CnH2n+1, n≥2) irrespective of the backbone structure. Kuhn segment increase [56] and considerable increase of thermal stability of the mesophase for cyclolinear atactic hexaalkylcyclotetrasiloxanes (ACTS) [57, 58] happen in the consequence of minimal increase of chain rigidity at transition from linear polyorganosiloxanes to atactic poly(hexaorganocyclotetrasiloxanes). Atactic methyl-substituted ACTS, as well as its linear analogue (PDMS) does not possess mesomorphous properties [57 – 59]. Further increase of poly(organosiloxane) chain rigidity by increasing the fracture of trans-units in ACTS macromolecules induces qualitative changes: occurrence of mesomorphous properties for methyl-substituted ACTS [59 – 61]. For the purpose of broadening conceptualization of mesomorphous properties display in polymers with tetrasiloxane rings in the backbone [62] copolymers, derived from ACTS, with alkyl subs-tituting agents in the ring and different length of dialkylsiloxane junction were synthesized by HFC reaction of 1,5-dihydroxyhexaalkylcyclotetrasiloxanes with α,ωdichloropolydialkylsiloxanes in the presence of hydrogen chloride acceptors in various solvents in accordance with the scheme as fol-lows:

234

O. Mukbaniani, G. Zaikov and T.Tatrishvili R2

R2 R

HO n R

+ nCI(SiR2O)m-1SiR2CI -HCI OH R2

R O(SiR2O)m R R2

Scheme 6

I

n

Where: R = Me, Et, Pr; m = 1, 2, 3. α,ω−dichloropolydialkylsiloxanes were synthesized by partial hydrolysis of diethyldichlorosilane and di-n-propyldichlorosilanes. It is found that cyclolinear hexapropylcyclotetrasiloxane copolymers with di-n-propylsiloxane units are not formed under current reaction conditions. In accordance with the results of gas-liquid chromatography studies, primary compounds enter the reaction completely, but the reaction conditions (temperature and diluter concentration) do not provide for sufficient chain propagation. All synthesized ACTS copolymers are completely soluble in usual organic solvents. The structure of copolymers was proved by the data of ultimate analysis, NMR and 29Si NMR spectra, chemical shifts of which are shown in Table 10. Table 10. Physical and chemical characteristics of PACS №

Copolymer

R

m

[η]*, dl/g

Yield, %

Cis:trans units relation in copolymer

1

MCTS***

Ме

0

0.17

80

88:12

2

MCTSS-1

Me

1

0.15

81

3 4 5

MCTSS-2 MCTSS -3 ECTS***

Me Me Et

2 3 0

0.16 0.13 0.26

75 70 -

29

Si chemical shifts δ, ppm (Irel)**

Dc -19.27 -19.31

Dl -

93:7

-19.51 (0.83) -19.58 (0.17)

95:5 95:5 70:30

-19.64 -19.67

-21.15 (0.03) -21.23 (0.26) -21.33 (0.70) -21.56 -21.64 -

-19.66 -19.65 7

ECTS-1

Et

1

0.08

75

70:30

-20.20 (0.65) -20.23 (0.35)

-21.92 (0.10) -21.95 (0.40) -21.95 (0.50)

8

ECTS-2

Et

2

0.09

80

70:30

-20.16

-22.07

9

ECTS-3

Et

3

0.09

47

70:30

-20.28

10

PCTS***

нPr

0

0/23

60

70:30

-21.86 (0.85) -21.98 (0.15)

-22.23 (0.33) -22.37 (0.67) -

T -65.74 (0.11) -65.53 (0.78) -65.77 (0.10) -65.12 (0.85) -65.30 (0.15) -65.30 -65.39 -66.61 -66.65 -66.97 -66.99 -66.63 (0.70) -66.89 (0.30)

-66.71 (0.70) -67.01 (0.30) -66.91 (0.70) -67.17 (0.30) -68.14 (0.15) -68.33 (0.85)

*

At 250C in toluene. ** Dc and Dl are chemical shifts for R2Si groups in the structure of rings (cyclic fragments) and linear fragments, respectively; T is chemical shift for RSiО1.5 groups. *** Corresponded polyhexaalkylcyclotetrasiloxane copolymers are shown for a comparison.

DSC investigations indicate that MCTSS-1 and MCTSS-3 are incapable of regulation. MCTSS-2 crystallizes and transits into an isotropic melt above Tmelt = +5°C. As concerns

Organosilicon Copolymers with Monocyclic Fragments …

235

ECTSS-1 and ECTSS-2, they are in the mesomorphous state below the isotropization temperature, Tiso, transiting into mesomorphous glass below glass transition temperature, Tg. Flexible junction length increase, m, decreases thermal stability of the mesophase, and in the case of m = 3 (ECTSS-3), to suppression of copolymer ability to transit into the mesophase, i.e. ability of copolymer to the long-range intermolecular regularity is completely suppressed due to the loss of ability to intramolecular regulation. However, sufficient length of flexible junction and considerable intermolecular overlapping make possible occurrence of close regularity between cyclic fragments both at intramolecular and intermolecular levels. This conclusion is based on occurrence of amor-phous dispersion in the angular area, close to θ1 value for poly(ethylcyclotetrasiloxane), on diffrac-tion patterns of ECTSS-3 at low temperatures. To put it differently, a tendency to close regulation by type of nematic diskophase, ND, is observed for ECTSS-3 [63]. MCTSS-1 and MCTSS-3 diffraction patterns, obtained in the temperature range of -130+40°C, and MCTSS-2 one, obtained above +25°C, are qualitatively identical to the diffraction pattern of homo-polymeric atactic MCTS. They contain two amorphous halos: the first is intensive one in the angular area of 2θ=9-120 (1/2∆ =1.2 ) with the maximum at 2θl and the second weak diffuse one in the area of 2θ=16–250. It is common knowledge [64] that for polyorganosiloxanes 2θ1 value characterizes the average intermolecular distance in amorphous component or isotropic melt. It is shown that in-terplane distances, dm, in copolymers decreases with increase of flexible junction length, m, and increases with the length of side framing, n. As flexible junction is introduced and its length is inc-reased, angular location of the maximum of the first amorphous halo (2θl) is shifted to the area of larger angles, and the glass transition temperature (Tg) of MCTSS decreases, approaching Tg of its linear analogue (PDMS) at m = 3. This means that decrease of polymeric chain rigidity with m inc-rease proceeds simultaneously with decrease of average intermolecular distances. As suggested in ref. [62], the tendency of ACTS copolymers to regulation is displayed on two inter-connected levels: intramolecular and intermolecular ones. On the one hand, cylindrical fragments tend to realize a conformation with the shortest intramolecular distances. On the other hand, this conformation provides for a disposition of side radicals, which may induce rather strong interaction between them to affect intramolecular regularity and stabilize a definite revolute configuration. Moreover, if isomers of organic polymers are stabilized by Vander-Waals detachment of valence unbonded atoms or radicals only, in the case of considered compounds, this mechanism is added by a factor, stipulated by the following feature of ACTS copolymer macromolecules: different nature of the backbone and side framing. Similar to linear analogues [65 – 70], side radicals in ACTS co-polymers will tend to form organic cover for coiled siloxane chain. For previously synthesized poly(methylcyclosiloxanes) with cyclic pentasiloxane and heptasiloxane fragments, no mesophase was observed. However, it should be noted that cyclolinear poly(organo-cyclotetrasiloxanes) with aliphatic substituting agents form a mesomorphous state, substituting agent length increase from methyl to propyl fragment inducing mesophase isotropization temperature increase, and at sufficient molecular mass poly(hexa-n-propylcyclotetrasiloxane) is present in the mesophase in the range from glass transition to decomposition temperature transiting into the me-sophase glass below the glass transition temperature [57]. These results gave grounds [72] to suggest that the introduction of aliphatic substituting agents (ethyl, propyl, etc.) into poly(organosiloxanes) with cyclic pentasiloxane fragments in

236

O. Mukbaniani, G. Zaikov and T.Tatrishvili

the linear backbone promotes mesophase formation and increases thermal stability. For this purpose, HFC re-action of 1,5-dichlorooctaethylcyclopenta siloxane with 1,3dihydroxytetraethyldisiloxane in the presence of pyridine, proceeding in argon flow in the temperature range from 25 to 50°C in accor-dance with the scheme shown below, was studied: Et2

Et

Et + xHO(SiEt2O)2H

x

CI

CI Et2

Et2

Et 2xPy

HO

O(SiEt2O)2 H

-2xPyHCI

Et2

Et2

Et

Et2

x

V

Scheme 7

After precipitation, polymer with [η]=0.07 with 36% yield was obtained. The structure of synthesi-zed polymer was detected based on the spectral data. X-ray and calorimetric studies of the polymer shows Tg=-127°C, i.e. introduction of a flexible jun-ction decreases Tg compared with poly(hexa-n-propylcyclotetrasiloxane) beadshaped polymer [57] and approaches it to Tg of linear poly(diethylsiloxane) (PDES) [73]. Above Tg, diffraction patterns of the polymer display a single sharp peak at 500С 2θ=10.13° (∆∼З0′). Dispersion remains un-changed up to isotropization at 35°C. The data obtained correlate with the results of DSC studies and thermal analysis. Taking into consideration temperature dependencies of angular dispositions of observed reflexes and atactic structure of the backbone, one may suggest that for synthesized polymer long-range positional order in the packing of gravity centers of macromolecules is realized in two directions only in the plane perpendicular to chain axes: in the whole temperature range below the isotropization point. The effect of methylcyclosiloxane fragments in dimethylsiloxane backbone on properties of copoly-mers and formation of the mesophase state was studied [74] by HFC reaction of 1,7-dichloro(dihyd-roxy)-1,7-diorganooctamethyl cyclohexasiloxane with α,ω−dihydroxy(dichloro)dimethylsiloxanes at equimolar ratio of the initial components in the presence of amines. The reaction proceeds as fol-lows: R O (Me2SiO) O (Me2SiO) H n 2 p HO Si Si Si Si + pY(SiMe2O)n-1SiMe2Y -2pAm.HCI O (Me2SiO)2 R X O (Me2SiO)2 R p VII R

O (Me2SiO)

2

X

2pAm

Scheme 8

Where: R = Me, Ph; n = 0, 1, 2, 3. In synthesized cyclolinear siloxane polymers (CLSP) the dimethylsiloxane unit was taken as a flexible spacer [74]. Table 10 shows temperatures and heat transitions in relation to the flexible spacers’ lengths. These polymers were found in the crystalline and thermotropic states, like trans-tactic poly-(decaorganocyclohexasiloxanes), but temperature range of the

Organosilicon Copolymers with Monocyclic Fragments …

237

mesomorphous state is considerably narrower; n increase to 3 gives completely amorphous polymers. This sharp decrease of isotropization temperature in CLSP with flexible spacers is not unexpected, since addition of dimethylsiloxane spacer instead of the hydrocarbon one has similarly led to a sharp decrease of isotropization temperature in liquid-crystalline polymers with classic mesogenic groups [75]. The authors studied the structure of decaorganocyclohexasiloxane polymer unit with the help of Stuart-Briegleb models and compared reflex variation with temperature at 2θ=9- 11°. Figure 10 shows CLSP unit resembling a disc with d1 =11.5 Å and height h=7.8 Å, introduced into the backbone as discshaped thin plates similar by thickness to interplanar distance d=8.4 Å, which was calculated from experimental data on the maximum position (refer to Figure 11).

Figure 10. Hypothetical model of decaorganocyclohexasiloxane polymer Chain [75].

Figure 11. Temperature dependence of interplanar distance, d, for decamethylcyc lohexasiloxane polymer: a – mesomorphous component; b – amorphous component, depending on the polymer chain tacticity: 1-atactic, 2-microtactic, 3-trans-microtactic

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O. Mukbaniani, G. Zaikov and T.Tatrishvili

Existence of the long-range order in the packing with the lower limit of the coherence area from 0.5h ≥ 400 Å indicates that the packing shown in Figure 10 only is possible for these intermolecular distances. It should be noted that distances of close values are realized in the ring itself; in this case, however, existence of so high long-range order is impossible, since intra- and intermolecular distances would alternate: first, they are different and secondly, differ. As a consequence, it is impossible to retain an unchanged long-range order in the broad temperature range of the mesophase. Existence of the single peak only follows from the suggested model. Thus, the order in the basic plane is realized in one direction only – perpendicular to the plane of the ring that is polymer chain unit, which is simultaneously perpendicular to the main axis of the polymer macromolecule. Table 11. Temperatures and heat transitions of cyclolinear poly (methylphenylsiloxanes) with flexible spacers [75]

4 5 6

p

nSiO

[η] in toluene dl/g

Tg, 0 С

0 1

0.15 0.13

-91 -88

2

0.14

-91

3 0 1

0.15 0.20 0.19

-90 -41 -59

2 3

0.15 0.14

-67 -80

Me

Ph

Tm, J/g

-53 -7-12 187 82107 52 -

Hm, KJ

Tiso, 0 С

5.5 17.6

49 67-97

10.0 3.6

-

7-57

1.3

13.8 16.8

427 137167 -

3.0 1.3

14.7 -

Hi J/g

-

HO

7 8

R

R

3

Me2 Me2

1 2

Polymer chain

Me2 O-(SiMe2O)n H R Me2

№

Comparison of the data shown in Figure 10 with d values from the diffraction pattern in Figure 11 indicate (Figure 11a) that the mesomorphous component (a narrow reflex), d, is independent of poly(decamethylcyclohexasiloxane) chain tacticity. Hence, irrespective of trans-tactic polymer abi-lity to crystallization, the mesophase temperature range changes insignificantly. At lower tempera-ture of –73°С only, a bending on the temperature dependence curve, d(T), of the mesophase peak occurs. Variation of d(T) dependence shape at the bending is accompanied by a considerable increase of the narrow reflex integral half-width and decrease of the integral intensity. In this temperature range, the interplanar distance, d, is comparable with the disc– decamethylcyclohexasiloxane unit–height (Fig-ure 10) due to close packing, leading to decreased long-range order areas [74,75]. Using the methods of amorphous halo separation from the narrow reflex, Figure 11b shows d(T) dependences for poly(decamethylcyclohexasiloxane) of different tacticity. Figure 11b indicates that tacticity variation affects the values and shape of d(T) dependence of amorphous halo. At 20°С, the difference of studied samples in d is insignificant, but at 197 -

Organosilicon Copolymers with Monocyclic Fragments …

239

247°С difference in the amorphous halo approaches 1 Å, approximately. The bending observed at the beginning of active melting of the mesophase is indicated by abrupt intensity drop of the mesophase peak. Thus, as follows from the analysis of d(T) dependence of amorphous dispersion, the polymer chain tacticity breakdown causes changes of packing in two directions only, where the long-range order is not realized, but the interplanar spacing is unaffected. As follows from d(T) dependence (Figure 11) of the mesophase peak and amorphous halo, intro-duction of phenyl substituting agents to organosilsesquioxane fragments in the organocyclohe-xasiloxane unit leads to the differences depending on the polymer chain tacticity, not only in the amorphous dispersion, but also in the mesophase peak position. Thus, the above data show the main factors responsible for mesomorphous state formation, which are, first, the increased conformational parameters and the Kuhn segment (A) of CLSP as a con-sequence of certain conformation of organocyclosiloxane unit, most likely, the folded ring confor-mation or any other ensuring, approximately, co-planar conformation of these cyclosiloxanes; se-conddddly, inclusion of organocyclosiloxane unit with symmetrical position into the polymer chain by para-position type; thirdly, the use of organic substituting agents ensuring amplification of both intra- and intermolecular interactions simultaneously capable of increasing the rigidity of the back-bone. The factors responsible for the mesomorphous state temperature range are: first, the polymer chain tacticity, perfect for the mesophase emerging in CLSP is the trans-tactic structure enabling to achieve the highest isotropization temperatures at low degrees of polymerization; secondly, growth of CLSP molecular weight leading, irrespective of the CLSP unit structure, to extended mesomor-phous state temperature range in CLSP. Thermal decomposition of branched chain methylsiloxane polymers has been studied before [5, 76-79]. Methylsiloxane rings and polycycles were detected as volatile products of the methylsiloxane resin pyrolysis [5,76-79]. The results indicate that pyrolysis decomposition of methylsiloxane resins is similar to that observed for methylsiloxane chain polymers [4]. The relation between the polymer structure and thermal degradation products can be interpreted in terms of this decomposition mechanism, but a resin of irregular structure does not provide proper system for studying this relation. Thermal decomposition products [80] of two methylsiloxane polymers of strictly regular and known structure were examined to clarify the mentioned relations. The polymers studied include di- and tri-functional structural units (i.e. (CH3)2SiO2/2 denoted as -D- and CH3SiO3/2 denoted as -T<) and involve cyclolinear chain structures, as follows: D (T2D6)n :

T

T

D

D

D

D

n

D

and D (T2D9)n :

T

T D

Structure 1

D

D

D

D

D D D n

240

O. Mukbaniani, G. Zaikov and T.Tatrishvili These structures are ensured by the method of synthesis used.

Figure 12. Cyclolinear methylsiloxane polymers’ pyrolysis products separated in OV-1 gas chromatographic phase [80].

Figure 13. A plot of retention time against retention time for pyrolysis products on temperature programmed columns coated with OV-1 and OV-17 stationary phase, respectively [80]

Thermal decomposition of investigated cyclolinear methylsiloxane polymers at 350°C gives cyclic methylsiloxane oligomers. Generally, the polymer (T2D6)n decomposes to D3, and polymer (T2D9)n to D3, D4, D5 etc., similar to poly(dimethylsiloxane), but the degree of conversion is very low at this temperature. At higher temperatures several polycyclic compounds are also produced from both po-lymers. Figure 12 shows relative amounts of products, produced by pyrolysis at 550°C due to GLC results. The gas chromatographic peak areas are related to the peak area of the most abundant pro-duct. The product distribution in the temperature range of 450-600°C does not vary significantly with pyrolysis duration or pyrolysis temperature. The author identified ten of fifteen main products by comparing gas

Organosilicon Copolymers with Monocyclic Fragments …

241

chromatographic retention times with these pure standard substances on three dif-ferent GC stationary phases. Standard polycyclic siloxanes were obtained from methylsiloxane resin by pyrolysis followed by preparative gas chromatography.

Figure 14. A plot of retention time against retention time for the pyrolysis products on temperature programmed columns coated with QF-1 and OV-17 stationary phase, respectively

Their identity was proved by mass spectrometry, 29Si NMR spectroscopy and X-ray diffraction patterns [76-79]. Standards are not available for some important products, but these seem to be ho-mologous with the products identified. This is indicated by straight lines which join the points given by the retention time values of the products measured on two different stationary phases with a li-near temperature program (Figures 13 and 14). The products identified are represented by circled points in the Figures. Examining the structures and amounts of the pyrolysis products, one may observe some correlation between the polymer structure and the pyrolysis products. Pyrolysis products are either cyclic or bi-cyclic methylsiloxanes ranging from 3 to 9 siloxane units. Pyrolyzate of the polymer (T2D9)n displa-ys higher quantity of cyclic products than in that of (T2D6)n. Relative quantities of cyclic products D3, D4 and D5 in the pyrogram of (T2D9)n are similar to these found in the pyrogram of poly(dime-thylsiloxane), but smaller quantity of D4 and D5 from (T2D6)n was observed. All-important pyrolytic products belong to a homolog series of siloxane units (see Figures 13 and 14). Three series were found for double rings shown in Table 12. None of the products include more than two T units. Quantitative evaluation of the total amounts of T and D units, found in the pyrolyzate, gives a T/D ratio corresponded to that in the original polymer. For the conversion of peak area values into weights authors used reflex factors for the Flame Ionization Detector [81]. Structures of volatile degradation products show that all these molecules were detached from the cyclolinear polymer by the mechanism first suggested for poly(dimethylsiloxane) by Thomas [4]. In this mechanism, degradation starts with formation of an intermediate fourcentered structure, and then two siloxane bonds involved are rearranged.

242

O. Mukbaniani, G. Zaikov and T.Tatrishvili Table 12. Homolog series of cyclolinear methylsiloxane copolymer pyrolysis Composition

Series I T

T2D3

D

Series II T D D

D

D

T

Series III _

D

T

T

T2D4

D

D

D T

D

T2D6

D

D D

T

D

T

D

_

D D

D T

D

D

D D D D

D

D

D D T D T

T

D

T

D

D D D

D

D

D T

D T T

D D

T T

D

D

D D

T

T2D5

T

D

T T

D D

D

_

D

T2D7

D

D

D D

D T D T D

D

For poly(dimethylsiloxane) chain, resulting volatile product represents an oligomer ring. Similarly, D3, D4, D5 cyclic oligomers are detached from the linear part of studied cyclolinear methylsiloxanes. When the siloxane bond rearrangement between two linear segments, bonded to the same ring of the polymer takes place, double ring of the Series I can be detached as follows:

O O

Si

Si Si

Si

Si

O........

O

Si O

O

O

O

Si

O

Si........

Scheme 9

In T and D symbols: T D

D

....

D

D

....

D T

Scheme 10

D

T D D D D + D T

... D ...

Organosilicon Copolymers with Monocyclic Fragments …

243

may result from such inter- or intramolecular bicycles of Series II may form similarly, but the macromolecular segment, in which the siloxane bond rearrangement takes place has to include a triatomic siloxane ring: ...... T

T

.....

D Structure VIII

This modified molecular segment may result from such inter- or intramolecular rearrangement, as follows: ....

...

D

T D

D

... D

D D D

T

T

... D

D T D

... D

... D

D

D

...

...

D

T + D T D ... ... D

+

D

D D

...

Scheme 11

As a consequence, Series II products are assumed to be the products of three consecutive re-arrangement steps. Distinct double rings were also found among the pyrolysis products. Their formation can be desc-ribed in terms of bond rearrangement between the linear part and the adjacent ring of the polymer, as follows: D D D

D

D T D D T

D

....

D D

D T D T

D ....

D

+

D

....

D

....

D D

Scheme 12

In this reaction (scheme 12) two cleavages occur simultaneously. The absence of products with more than two T units indicates that none of secondary reactions of the primary products takes place. Under the pyrolysis conditions, the authors used stoichiometric composition of total pyro-lyzate similar to that of the polymer. In addition, no change in functionality of siloxane units takes place, which correlates with the author’s earlier results [77]. Accordingly, the structure of degradation products is closely connected with the macromolecular one. The original linear segments of the macromolecule appear in the pyrolyzate as cyclic oligo-mers, and the branching points are detached with adjacent fragments as polycyclic rings.

244

O. Mukbaniani, G. Zaikov and T.Tatrishvili

The ratio of mono- and double ring products’ quantities characterizes the average frequency of branching points in the polymer network. The exact description of structures of double ring products may help in distinguishing distribution of the branching points, and thus the microstructure of me-thylsiloxanes. The above discussion indicates that synthesized CLSP with phenyl framing groups are characterized by high thermal oxidative stability and easy processing to articles. That is why these substances we-re suggested for production of specific rubbers [12]. For the purpose of increasing selectivity of immovable phase for complete and selective separation of organic compounds and complex mixtures of organosilicon compounds by gasliquid chroma-tography method, CLSP of the following general formula was suggested [82]: Ph Ph Me O (SiMe2O)n H Me

HO Ph

Ph

x

Structure 1

Where: n = 3 - 20; x = 10 - 100. As the immovable phase, CLSP was applied to N-AW chromaton carrier in 20% quantity of its mass. The phase peculiarity to alcohols of the fatty sequence is shown on the example of synthetic alcohols C10 – C21 fraction separation in the temperature range from 100 to 270°C (at 4 deg/min rate) without preliminary transfer to volatile derivatives. In spite of the known phases, the advantage of suggested selective immovable phase is the possibility of selective analysis of various classes of organic and organosilicon compounds. Of spe-cial attention should be peculiarity of the phase to separation of cyclic and naphthene hydrocarbons, amines and alcohols with preservation of high thermal stability. Table 13 shows comparative data on Mac-Reynolds constants for a series of universal non-polar phases and high parameters of suggested phase. Table 13. Comparative data on Mac-Reynolds constants Immovable phase SE-30 SKT SE-54 DPOC Suggested CLSP naphthene phase (n = 3)

Х′ 15 17 33 86 95

Mac-Reynolds constants У′ Z′ И′ 53 44 64 57 46 67 72 66 99 130 134 181 135 120 185

S′ 41 45 67 154 145

Note also that in spite of the suggested phase, immovable phases considered give no opportunity to separate many classes of chemical compounds. In particular, amines and alcohols can be separated on these immovable phases, if transferred to volatile derivatives

Organosilicon Copolymers with Monocyclic Fragments …

245

only; cyclic and naphthene amines and alcohols cannot be separated, and complete separation of complex mixtures of organosilicon compounds cannot be performed.

2. CYCLOLINEAR COPOLYMERS WITH CYCLIC CARBOSILOXANE FRAGMENTS IN DIMETHYLSILOXANE BACKBONE Cyclolinear copolymers containing cyclic carbosiloxane fragments in dimethylsiloxane backbone were synthesized by HFC reaction of dichloro-containing organocyclocarbosiloxanes with α,ω−di-hydroxydimethylsiloxane. Copolymers were synthesized in 60 – 70% solution of anhydrous toluene both in the presence and in the absence of pyridine (hydrogen chloride acceptor) at 20 - 25°C. It is found that at HFC proceeding without acceptor, increase of dimethylsiloxane unit length and volume of the cyclic fragment decrease conversion by hydrogen chloride. In both cases, the reaction proceeds by the scheme as follows [14, 83]: R R O R SiMe2 C2H4 Me2Si C2H4 Si O (SiMe2O)n H + O x Si Si + xHO(SiMe2O)nH -HCI HO Si C2H4 O CI CI O O Si Si O O R Si RO m Si m O Ph 2 Ph2 x Si Ph2 m X VIII, IX R

Scheme 13

Where: m = 1 (VIII), 2 (IX); n = 2, 4, 10, 20, 37. When precipitated from toluene solution with methanol, synthesized copolymers are solid or viscous substances with ηspec = 0.07-0.30, well soluble in usual organic diluters, with regard to dimethylsi-loxane unit value. Table 14 shows the yield, Tg and viscosity parameters of cyclolinear carbosilo-xane copolymers. Table 14. Physical and chemical properties of cyclolinear carbosiloxane copolymers of structures VIII and IX № 1** 2 3 4 5 6 7 8 9 10 *

Copolymer

R HO

C2H4

m

R Si O (SiMe2O)n H

Si O

O Si Ph2

m

x

1 1 1 1 1 2 2 2 2 2

nSiO 2 4 10 20 37 2 4 10 20 37

Yeld, % 78 79 86 87 90 77 80 85 87 89

ηspes*

Тg,0С

d1, Å

0.08 0.11 0.18 0.25 0.29 0.09 0.12 0.18 0.26 0.30

-25 -60 -90 -105 -123 -10 -40 -75 -90 -123

8.82 7.24 7.21 9.80 7.25 7/24

In toluene at 25°С.** [η]=0.07;ΜSD=16.5x103; increment of refraction indexes dn/dc=0.28 cm3/g.

246

O. Mukbaniani, G. Zaikov and T.Tatrishvili

Comparatively reduced yield at low lengths of dimethylsiloxane unit (n= 2, 4) in reaction (scheme 14) is explained by partial proceeding of HFC reaction by intramolecular cyclization mechanism with formation of polycyclic structures. Similar to the reaction-scheme 1 a product of intramolecular condensation was extracted from the mother solution and additionally derived by direct synthesis. Thermogravimetric studies of cyclolinear copolymers have displayed their sufficiently high thermal oxidative stability. For short lengths of dimethylsiloxane unit, initial mass loss is observed at 260 – 280°C and 5% loss at 300°C. Above 750°C no mass loss variation is observed, which is apparently associated with formation of secondary structures. Thermal oxidative stability of copolymers with carbocyclosiloxane fragments in the backbone is similar to that of their pure siloxane analogues. Moreover, thermal oxidative stability of copolymers is decreased with increase of the volume of cyclic carbosiloxane fragment. Figure 15 shows dependence of the glass transition temperature of copolymers on cyclic carbosilo-xane fragment content in dimethylsiloxane backbone. Similar to copolymers from poly(dimethyl-phenylsiloxane) sequence [53], the effect of non-dimethylsiloxane units on Tg of copolymers with cyclic carbosiloxane fragments in the backbone is primarily observed at ~3% concentration of the latter.

Figure 15. Dependence of glass transition temperature of copolymers on mol% concentration of cyclic carbosiloxane (A) fragments: 1 –copolymers with m = 1; 2 – with m = 2

The Figure shows also that the effect of cyclic carbosiloxane fragments with m = 2 on Tg of studied copolymers is higher rather than for copolymers with m = 1; Tg of copolymers is increased with mol% concentration of cyclic carbosiloxane fragments. Diffraction patterns of copolymers with cyclic carbosiloxane fragments in the backbone are cha-racterized by the presence of two diffraction maximums typical of amorphous polymers. Data in Ta-ble 15 show that interchain distances, d1, decrease with the increase of dimethylsiloxane backbone length and at n = 37 reach the value typical of PDMS. Simultaneously, the increase of cyclic frag-ment volume in copolymers induces a considerable increase of d1. One more interesting feature of these copolymers is that initial difunctional cyclic organocarbosilo-xanes can be derived easily, and copolymers themselves contain reactive

Organosilicon Copolymers with Monocyclic Fragments …

247

cyclic carbosiloxane frag-ments capable of cross-linking without liberating volatile compounds [84].

3. ORGANOSILOXANE COPOLYMERS WITH HETEROCYCLIC FRAGMENTS IN THE DIMETHYLSILOXANE BACKBONE It has been shown in the literature [85] that introduction of arylene fragments into the dimethyl-siloxane backbone increases thermal oxidative stability of copolymers. For the purpose of synthe-sizing and studying properties of copolymers with 1,3-diorgano-1,3-disila2-oxaindane fragments in the backbone [85, 86], HFC reaction of 1,3-dichloro-1,3diphenyl(dimethyl)-1,3-disila-2-oxaindane with α,ω−dihydroxydimethylsiloxanes, dihydroxydiphenylsilane and 1,4-bis(hydroxydimethylsilyl)-benzene both in the presence and in the absence of pyridine (hydrogen chloride acceptor) was investigated [87]. Initial 1,3-dichloro-1,3-diphenyl(dimethyl)-1,3-disila-2-oxaindanes were synthesized by high-tem-perature pyrolysis of 1,3-dichloro-1,3-dimethyl(diphenyl)-1,3-diphenyldisiloxane [88] in the inert medium. HFC reaction of 1,3-dichloro-1,3-diphenyl-1,3-disila-2-oxaindane with dihydroxydiphen-ylsilane or 1,4-bis(hydroxydimethylsilyl)benzene proceeded with different ratios of reagents, which gave dihydroxy-containing oligomers with different transformation level (m=6-18). Some paramters of these oligomers are shown in Table 15. Further on, they were used for deriving block-copolymers of the (AB)mCn type. HFC reaction of 1,3-dichloro-1,3-diorgano-1,3-disila-2-oxaindane with α,ωdihydroxydimethylsiloxanes proceeded at equimolar ratio of initial components. In both cases, it proceeds in accordance with the scheme as follows:

R O R y CI Si Si CI + xHO-A-OH -HCI

R R O O A Si H O Si

OH m

XI

Scheme 14

Where: А=-Me2Si-C6H4-SiMe2-, R=Ph, x=y, m≈18 (XI1); А= -R’2Si-: R’=Ph; x≠y; m≈6,9 (XI2); А= -(R’2SiO)n-1R’2Si-: R=Me, Ph; R’=Me, (x=y), n=2,4,8,20,37 (XI3). If the reaction proceeds in 60 – 79% toluene solution at 20 – 25°C in the absence of acceptor, final conversion by hydrogen chloride decreases from 70% (n = 2) to 54% (n = 4) with increase of the length of dihydroxydimethylsiloxane unit. Methyl radical substitution by phenyl one at the atom of silicon in silaindane ring also decreases conversion by hydrogen chloride from 62% (n =2) to 43% (n = 4). High conversion by hydrogen chloride at low n of dimethylsiloxane backbone can be ex-plained by increased reactivity of ≡Si-CI bond, which is apparently associated [89] with a decrease of the valence angle of ≡Si-О-Si ≡ bond in 1,3disila-2-oxaindane. Lower reactivity of silaindane fragment with phenyl framing at atoms of silicon is explained by both steric effect and inductive influence of the framing groups. That is why for synthesizing high-molecular copolymers, HFC reactions were studied in the

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O. Mukbaniani, G. Zaikov and T.Tatrishvili

presence of pyridine. Re-precipitated copolymers are transparent or slightly opalescent products, well soluble in different organic solvents. Some physical and chemical parameters and yields of synthesized copolymers are shown in Table 15. Table 15. Physical and chemical parameters and yields of (oligomers) copolymers with 1,3-diorgano-1,3-disila-2-oxaindane fragments in the backbone of the structure XI

1

XI1

Ph

(19)

89

ηspec at 25°С 0.21

2

XI2

Ph

(6)

88

0.07

3

2

№

Copolymer (oligomer) unit

R

Yield, %

Тg , 0 С

d1, Å

Μωх10-3

215226 83-88

10.42

4.75

10.41

2.99

Ph

(9)

85

0.09

91-96

10.42

4.49

4

Me

2 4

-

-

Me Me Me Ph

8 20 37 2

7.24 8.81

144.1 29.8

Ph

4

-43 -78 -93 -118 -123 +11 -40

36.4

Me

-

-

Ph Ph Ph

8 20 37

0.14 (0.06) 0.16 (0.07) 0.18 0.26 0.31 0.13 (0.05) 0.15 (0.06) 0.18 0.29 0.39

8.60

5

76 (53) 79 (56) 86 90 90 78 (53) 80 (57) 82 86 90

-

87.9 -

6 7 8 9 10 11 12 13

XI

n (m)

R

R

O Si

Si

O(SiMe2O)n

x

-57 -87 -123

Note: Shown in brackets are parameters of copolymers derived in the absence of acceptor.

Data shown in Table 15 indicate that the yields of copolymers – the products of HFC reaction with-out acceptor, are rather low. Moreover, the experimental values, detected by the ultimate analysis, are somewhat different from theoretical ones. This fact proves that besides basic HFC process, side homofunctional condensation of initial α,ω−dihydroxydimethylsiloxanes proceeds under the reac-tion conditions, which disturbs the ratio and decreases molecular mass. Slight underestimation of the yields of copolymers with disilaoxaindane fragments in the backbone at short lengths of dimethyl-siloxane unit (n=2, 4) is caused by simultaneous proceeding of intermolecular and intramolecular cyclization during HFC, the latter synthesizing two-ring compounds. To prove regular structure of obtained copolymers, copolymer 11 (Table 15) was fractionated into four fractions. The ultimate analysis of all four fractions gave values similar to calculated ones. 1H NMR spectrum of the copo-lymer displays a singlet reflex for methyl protons with chemical shift at δ≈0.15 ppm, and the ratio of methyl and phenyl protons found coincides well with the calculated one. In turn, this proves the reaction proceeding with the formation of copolymers of regular structure. These data coincide with the experimental results [90]. Thermogravimetric analysis of the copolymers has displayed 5% mass loss at 330-360°C. Basic degradation process proceeds in the temperature range of 420 - 550°C, and above 620°C mass chan-ge curves become supersaturated. Thermal oxidative stability of

Organosilicon Copolymers with Monocyclic Fragments …

249

copolymers with disilaindane fragments in the dimethylsiloxane backbone is higher than for copolymers with cyclic carbosiloxane fragments in the backbone. Thermomechanical studies have shown that the effect of disilaindane fragment on the dimethyl-siloxane backbone is negligible, and Tg of the copolymer, even in the presence of tetramethylsilo-xane units, remains below zero at the methyl framing, whereas phenyl framing in copolymer 9 gives Tg = +11°С. Expansion of the linear fragment length decreases Tg down to Tg of PDMS (-123°С). Similar to the case of poly(dimethylphenylsiloxane) copolymers [91], Tg is linearly increased with concentration of non-dimethylsiloxane units in them. Note also that for copolymers 4 – 8 (Table 15), Tg dependence on disilaindane fragment content in them is close to that on the content of diphenylsiloxy units in poly(dimethylphenylsiloxane). For copolymers 9 – 13 (Table 15), increase of mol% concentration of disilaindane fragments induces sharper increase of Tg. X-ray diffraction studies have shown that diffraction patterns of all studied copolymers possessing disilaindane fragments in the backbone display two diffraction maximums: d1 = 7.24 - 8.81 Å and d2 = 4.45 Å, typical of amorphous polymers. Substitution of methyl framing by phenyl one in silaindane ring is accompanied by an increase of interchain distance. Analysis of diffraction patterns obtained proves the increase of interchain distance in copolymers with concentration of disilaindane fragments in them.

4. POLY(ORGANOCARBOSILOXANES) WITH CYCLIC SILOXANE FRAGMENTS IN THE MAIN BACKBONE Besides HFC reaction of preliminarily prepared cyclic organosiloxanes with functional groups and difunctional organosilicon compounds, which give an opportunity to preserve cyclic groups in the polymeric backbone, hydride polyaddition is also widely used, which proceeds under soft conditions and does not involve cyclic structures, introduced into the backbone. For the purpose of synthesizing poly(carbosiloxanes) with cyclic tetrasiloxane fragments in the me-thylsiloxane backbone, hydride polyaddition of divinylorganocyclosiloxane by dihydridedimethylsi-loxane was studied [92]. Polymers were synthesized in argon at 1:1 molar ratio of the initial reagents in the absence of diluter or in inert organic solvent (toluene) at 100 - 110°C. The reaction temperatu-re was selected at the level causing no scission of organosiloxane rings. Platinum-hydrochloric acid, double added to the reaction mixture in amount 1–1.5×10-5 g of H2PtCl6x6H2O per 1 g of the initial mixture, was used as the catalyst. A half of this amount was added before the reaction initiation, and the second half 25–140 hours after beginning of heating. Platinum-hydrochloric acid was added in the form of 0.01 M solution in tetrahydrofuran. Isopropyl alcohol, used as diluter for H2PtCl6x6H2O, decreased relative viscosity of synthesized polymers, apparently, due to proceeding of side alko-xylation reaction: ≡Si-H+HOC3H7 → ≡Si-O-C3H7 +H2 (Scheme 15) Linear poly(organocarbosiloxanes) with cyclic structures in the backbone were synthesized in ac-cordance with the following scheme [92]:

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O. Mukbaniani, G. Zaikov and T.Tatrishvili

x [Me2SiO]2[MeVinSiO]2 +x H(SiMe2O)n-1SiMe2H

H2PtCI6

Me2 Si Me Me O O CH2-CH2 Si Si-CH2CH2-(SiMe2O)n-1SiMe2 O O Si Me2

x

XII

Scheme 16

Where: n = 0÷200. Synthesized polymers represent viscous and highly viscous colorless transparent liquids, soluble in cyclic hydrocarbons and lower eaters. The effect of reaction proceeding in an inert organic solvent (for example, toluene) on inherent viscosity of derived polymer is negligible. Obtaining of high vis-cosity values in the presence of solvent requires just longer-term heating up of the reaction mixture. To the authors’ point of view, polymers of such structure, possessing cyclic fragments in the back-bone, are of interest due to their high reactivity. For example, these polymers are capable of easy formation of cross-linked structures in anionic catalysts. Initial divinylhexamethylcyclotetrasiloxa-ne was synthesized by combined hydrolysis of dimethyldichlorosilane and methylvinyldichlorosila-ne. Despite the application of efficient rectification columns and analytical chromatograph with preparative add-on device, the attempts of the authors to separate isomeric 1,3- and 1,5-divinylhexamethylcyclotetrasiloxanes, which may be formed in cooperative hydrolysis, have failed. That is why isomeric structural groups as follows (XIII) may also be present in synthesized polymers: Me

Me CH2-CH2 Si

O

O Me2Si

Si-CH2CH2-(SiMe2O)n-1SiMe2 O

O

SiMe2

x

Structure XIII

Semi quantitative assessment of the ratio of isomeric 1,3- and 1,5-cyclic structures in synthesized polymers with the help of NMR spectra was performed, which was found 1:1. In a series of processes variation of functional groups content (≡Si-H due to IRspectroscopy data) during reaction proceeding and type of the increase of reaction mixture specific viscosity were studied. Maximal viscosities of polymers ([η]=0.17-0.97 dl/g) are reached after 50–160 hours of heating and in majority of cases depend on the length of α,ωdihydridedimethylsiloxane chain and purity of initial compounds used. Studies of IR spectra of synthesized poly(organocyclocarbosiloxanes) and preliminary experiments on long-term heating of the mixture of initial hexamethyldivinylcyclotetrasiloxane isomers under polyaddition conditions allow a suggestion that polymers are synthesized due to hydride polyaddi-tion proceeding with preservation of structures of

Organosilicon Copolymers with Monocyclic Fragments …

251

initial compounds, but not polymerization of cyc-lic hexamethyldivinylcyclotetrasiloxane. The presence of organocyclotetrasiloxane fragments in the structure of synthesized poly(organocyclocarbosiloxanes) may be proved by their transition into non-fusible, insoluble state due to polymerization of organosiloxane cycles existing in the polymer structure. As reprecipitated polymers are heated at 100-110°C in the presence of 0.001–0.01 wt.% of anionic polymerization catalysts, viscosity is considerably increased and gel is formed. Varying length of alkylenesiloxane bridge between organocyclotetrasiloxane fragments of poly(organocyclo-carbosiloxanes) backbone, one may change the average distance between cross-link points and, con-sequently, properties of cross-linked polymers formed. Hydride polyaddition between 1,5-divinyl-1,5-dimethyl-3,3,7,7-tetraorganocyclotetrasiloxane and methylphenylsilane has been studied [93]. All attempts to separate initial divinylorganocyclotetrasi-loxanes into cis- and transisomers have failed. Thus, according to NMR data, initial divinylorgano-cyclotetrasiloxanes represent a mixture of cis- and transisomers. The reaction proceeds as follows: R' R" CH2=CH2 Me

Me x

+ xH-Si-H

CH2=CH

Me R' R"

Me H2PtCI6 0

T C

R' R" Me CH2CH2 Si CH2 Ph Me

CH2

Ph

R' R"

x XII

Scheme 17

Where: R′ = R′′ = Me = Ph; R′ ≠ R′′. Polyaddition was carried out at 60–70°C, and at the final stage the mixture was heated up to 100°C. The catalyst in amount 5×10-4 Pt mol/mol was added to vinylcyclosiloxane, heated up to 50°C. Some parameters of synthesized copolymers are shown in Table 16. Table 16. Physical and chemical parameters of poly(organocarbosiloxane) of cyclolinear structure Copolymer

No

1 2 3

Me

R' R"

CH2

R′

R′′

[ η], dl/g

Me

Me Ph Ph

0.08 0.06 0.04

Me Me Ph CH2CH2 Si CH Ph Me

Tdegr* of 5% mass loss

Tdegr* of 5% mass loss

Тg, °С

240 320 370

52 45 41

-7 26 13

R' R" *

TGA data on polymers processed by heptamethylvinylcyclotetrasiloxane. Copolymer struc-ture was determined from 29Si NMR spectral data.

For the purpose of synthesizing carbosiloxane copolymers with organocyclopentasiloxane fragments in the dimethylsiloxane backbone, hydride polyaddition of α,ωdihydridedimethylsiloxanes to l,5-ivinyl-l,5-dimethylhexaphenylcyclopentasiloxane in the

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presence of platinum hydrochloric acid as a catalyst was studied at temperatures below 100°C: 75°C, 80°C and 85°C. Forasmuch as the initial 1,5-divinyl-1,5-dimethylhexaphenylcyclopentasiloxane represents a mixture of cis- and transisomers (at the ratio copolymers derived from them are atactic. Preliminary heating of initial compounds within the temperature range of 80 - 95°C in the presence of the catalyst indicated that under these conditions organocyclopentasiloxane fragments are not polymerized. The reaction proceeding was detected by a decrease of amount of active ≡Si-H groups. It was obser-ved that the rate and depth of polyaddition decrease with the increase of α, ωdihydridedime-thylsiloxanes chain length. Hydride polyaddition proceeds in accordance with the following scheme [94, 95]: Ph2

Vin x Me

Me CH2 + xH(SiMe2O)n-1SiMe2H H2PtCI6 0 Vin TC Me

Ph2 Ph2

Ph2 Me CH2CH2 (SiMe2O)n-1SiMe2CH2 Ph2 Ph2 x XIV

Scheme 17

Where: n = 2 – 23. As a result of the reaction, copolymers with ηspec = 0.09 – 0.26 are obtained, which are liquid or glassy light-yellow products, soluble in ordinary organic solvents. Some physical and chemical parameters and the yield of copolymers are listed in Table 17. As indicated by the data in the Table, in the case of short lengths of the dimethylsiloxane backbone, n, the yield of copolymers is low. This may be explained by the fact that besides intermolecular reaction, intramolecular cyclization proceeds forming a polycyclic structure. This conclusion is in agreement with data from the literature [12 - 17]. Table 17. Physical and chemical parameters of structure XIV carbosiloxane copolymers containing cyclopentasiloxane fragments

nSiO

Yield, %

Reaction T,0C

η*sp

Tg, 0 C

d 1, Å

5% mass losses

Μωx10-3

1

2

75

85

0.09

0÷-2

9.20

320

189

2 3

4 6

80 92

85 75

0.14 0.15

-22 -

-

-

-

6

93

80

0.18

-

-

-

-

№

3′ 3′′

Copolymer

CH2

Ph2 Me

Me Me C2H2 (SiO)n-1SiCH2 Me Me

Me Ph2 Ph2

4 5 *

x

6

95

85

0.20

-53

-

295

211

12 23

95 96

85 85

0.24 0.31

-82 -123

7.21

285

236

In toluene at 250C

The amount of active ≡Si-H groups was decreased during proceeding of hydride polyaddition. It was shown, that the rate of hydride polyaddition increases with temperature (at one and the same values of dimethylsiloxane units, n), but on the other hand, with an

Organosilicon Copolymers with Monocyclic Fragments …

253

increase of the length of dimethylsilo-xane links (n) at the same temperatures, the rate of hydride polyaddition decreases. It was found that polyaddition is the second order reaction. The reaction rate constants and the acti-vation energy were calculated: k75oC≈1.4004x10-2, k80oC≈1.965x10-2, k85oC≈2.559x10-2 mole/l⋅sec. Ea=62.1 kJ/mol, respectively. 1 H NMR spectra of copolymers indicate that catalytic hydride polyaddition mainly proceeds by the Farmer rule with formation of dimethylenic bridges. In these spectra a reflex of –СН2-СН2- group with chemical shift δ = 0.34 ppm is observed; it is indicated that hydride polyaddition partly (about 6 - 7%) proceed by the Markovnikov rule. Cyclolinear carbosiloxane copolymers with 1,7- and 1,5-disposition of dimethyloctaphenylcyclohe-xasiloxane fragments in the dimethylsiloxane backbone were synthesized by hydride polyaddition of α,ω−dihydridedimethylsiloxane to 1,7-divinyl-1,7dimethyloctaphenylcyclohexasiloxane and 1,5-divinyl-1,5dimethyloctaphenylcyclohexasiloxane in the presence of a catalyst. Polyaddition reacti-ons were studied below 100°C. It was also indicated that under these conditions polymerization or polycondensation of initial compounds does not take place. Polyaddition proceeds in accordance with the following scheme [95 - 97]: Me x Vin

O(SiPh2O)l

Si + xH(SiMe2O)n-1SiMe2H

Si

Me

Me

O(SiPh2O)m Vin

H2PtCI6

O(SiPh2O)l

Me

0

Si

TC CH2

Me

C2H4 (SiO)n-1SiCH2 Me Me Si

O(SiPh2O)m

Me XV, XVI

x

Scheme 18

Where: m = l = 2 (XV); n = 2 – 23; l = 1, m = 3 (XVI); n = 2 - 23. Forasmuch as 1,7- and 1,5-divinylcyclohexasiloxanes, used in polyaddition, represent mixtures of cis- and trans-isomers of the approximate 52:48 ratio, synthesized copolymers are atactic. Repre-cipitation of copolymers from toluene solution by methyl alcohol has given viscous or solid (with regard to the value of flexible junction) transparent products with ηspec = 0.09 - 0.29, well soluble in different organic solvents. It is found that at short length of dimethylsiloxane unit (n ≤ 4), copo-lymer yields are slightly decreased that may be explained by partial proceeding of hydride polyad-dition by intramolecular cyclization mechanism (see Tables 18 and 19). After solvent removal from the mother solution of re-precipitated copolymer 1 (Table 18), a semi-crystalline compound with the molecular mass equal ~1100 was obtained [96, 97]. The product of intramolecular cyclization of 1,7-divinyl-1,7-dimethyloctaphenylcyclohexasiloxane and 1,3-dihyd-ridetetramethyldisiloxane of the following structure only may display the current molecular mass: because divinylorganocyclohexasiloxane of the trans-structure participates in formation of macro-molecular chain. Structure and composition of synthesized cyclolinear carbosiloxane copolymers were determined by functional and elementary analysis, IR and NMR spectral data. Some parameters of copolymers are shown in Tables 18 and 19.

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A reflex with chemical shift at δ=0.35 ppm typical of –СН2-СН2-group is observed in 1Н NMR spe-ctrum of copolymer 1 (Table 18). This indicates that polyaddition proceeds pursuant to the Farmer rule. A duplet centered at δ = 1.06 ppm, corresponded to methyl protons in =СН-СН3 group, is also observed in the spectrum. Based on the ratio of intensities, it was concluded [96, 97] that polyad-dition partly proceeds by the Markovnikov mechanism (6 –8%). A complex multiplet with chemi-cal shift at δ=5.6-6.2 ppm typical of vinyl protons not entered polyaddition reaction, and a singlet for ≡Si-H protons with chemical shift at δ = 4.4 ppm, not participated in the reaction, too, were ob-served in the spectra. Hydride polyaddition proceeded at different temperatures. It was shown, that variations of ≡Si-H bond concentration during polyaddition of α,ω−dihydridedimethylsiloxane (n=6) to 1,7-divinyl-1,7-dimethyloctaphenylcyclohexasiloxane and 1,5-divinyl-1,5-dimethyloctaphenylcyclohexasiloxane. It is observed that hydride polyaddition depth is increased with the reaction temperature. Moreover, the effect of 1,7- or 1,5-disposition of vinyl groups in cyclohexasiloxane fragments is the negligible factor for their reactivity. It is found that at the initial stages, polyaddition represents the second order reaction. Activation energies for 1,7-divinyl-1,7-dimethyloctaphenylcyclohexasiloxane and 1,5divinyl-1,5-dimethyloc-taphenylcyclohexasiloxane were also calculated: Еa=66.7 and Ea=69.7 kJ/mol, respectively. Obvi-ously, these values are very close. X-ray diffraction studies have indicated that copolymers are single phase amorphous systems, and maximal interchain distance is observed for short dimethylsiloxane unit length (n=2); hence, for co-polymer 1 (Table 19), d1=9.60 Å. This value is slightly greater than the interchain distance of car-bosiloxane copolymer 1 (Table 18) with 1,7-disposition of cyclohexasiloxane fragment in the dime-thylsiloxane backbone (n=2). As flexible junction length is increased, d1 decreases and approaches the interchain distance in PDMS; it increases with the volume of cyclic fragment at the same lengths of flexible dimethylsiloxane unit, i.e. at transition from cyclopentasiloxane to cyclohexasiloxane fragment. Thermogravimetric studies of carbosiloxane copolymers have indicated 5% mass loss of the com-pounds in the temperature range of 250 - 260°C. The main degradation process proceeds in the ran-ge of 380 - 630°C, and above 700°C the mass loss is not observed. It is found that thermal oxidative stability of copolymers is decreased with increase of the cyclic fragment volume, i.e. at the transi-tion from cyclic pentasiloxane to hexasiloxane fragments in cyclolinear carbosiloxane copolymer. It is also found that carbosiloxane copolymers with 1,7- and 1,5-disposition of cyclic hexasiloxane fra-gments in the backbone are characterized by almost identical thermal oxidative stability. Thus, was concluded [96, 97] that the effect of 1,7- or 1,5-disposition of cyclic hexasiloxane frag-ment in carbosiloxane copolymer is negligible for thermal oxidative stability of copolymers (Figure 16). On the other hand, compared with pure siloxane analogues, thermal oxidative stability of carbo-siloxane copolymers is lower. Thermogravimetric studies have displayed that the cyclic fragment causes a considerable effect on carbosiloxane copolymer at n=12 only, and at n=23 no effect of cyclic fragment on the glass tran-sition temperature of the copolymer is observed. Figure 17 shows dependence of Tg on the length of dimethylsiloxane unit for cyclolinear carbosiloxane copolymers.

Organosilicon Copolymers with Monocyclic Fragments …

255

Figure 16. Thermogravimetric curves of carbosiloxane copolymers: 1 – copolymer 4 (Table 19) with 1,5disposition of cyclic hexasiloxane fragment in the backbone; 2 –copolymer 1 (Table 18) with 1,7-disposition of cyclic hexasiloxane fragment in the backbone; 3 – copolymer 1 (Table 17) with cyclic pentasiloxane fragment in the back bone.

Figure 17. Dependence of Tg for cyclolinear carbosiloxane copolymers on the length of dimethylsiloxane unit: 1 – copolymer with 1,7-position of cyclic hexasiloxane fragment; 2 – copolymer with 1,5-position of cyclic hexasiloxane fragment.

It has been found that expansion of the cyclic fragment volume at the same length of dimethylsilo-xane unit, i.e. introduction of a single diphenylsiloxane unit, Tg of the copolymer is increased by ~10°C. It is also shown that the effect of 1,7- or 1,5-disposition of cyclic hexasiloxane fragment on Tg of the copolymer is negligible, which conform to the previous results on pure siloxane copoly-mers.

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Table 18. Physical and chemical parameters of carbosiloxane copolymers with 1,7disposition of cyclic hexasiloxane fragments in the dimethylsiloxane backbone (structure XV)

№

1 2 3 3′

Copolymer

Me

Me

Ph2 Ph2

3′′ 4 5 *

Ph2 Ph2

nSiO

Me Me C2H2 (SiO)n-1SiCH2 Me Me x

Reaction T,0C

Yield, %

η*sp

Tg, 0 C

d1, Å

5% mass losses

Μωx 10-3

2 4 6 6

74 80 94 94

90 90 80 80

0.10 0.12 0.17 0.17

+5 -10 -

9.31 -

280 -

174 -

6 12 23

95 96 95

85 90 90

0.18 0.23 0.29

-40 -68 -123

8.81 8.40 7.24

280 260

194 231

In toluene at 25°C.

Table 19. Physical and chemical parameters of carbosiloxane copolymers with 1,5– position of cyclic hexasiloxane fragments in the dimethylsiloxane backbone (structure XVI)

№

1 2 3 3′

Ph2 Me Me Me C2H2 (SiO)n-1SiCH2 Me Me Ph2 Ph2 Ph2

Me

3′′ 4 5 *

Copolymer

nSiO

Yield, %

Reaction T,0C

η*sp

Tg, 0 C

d 1, Å

5% mass losse s

Μωx 10-3

2 4 6 6

72 84 86 89

10 85 80 90

0.09 0.11 0.15 0.18

+8 -12 -

9.60 -

270 -

159 -

6

94

100

0.15

-38

8.90

265

180

12 23

95 95

100 100

0.22 0.28

-72 -123

8.34 -

260

210 -

In toluene at 25°C.

5. CYCLOLINEAR COPOLYMERS DERIVED BY POLYMERIZATION OF ORGANOBICYCLO-AND ORGANOTRICYCLOSILOXANES The above-mentioned materials indicate that cyclolinear organosiloxane copolymers are usually synthesized by homopolycondensation and HFC reactions of difunctional organocyclosiloxanes or organopoly(cyclosiloxanes) with α,ω−dihydroxy(diamino, dichloro)diorganosiloxanes. As known from the literature, polymerization and copolymerization of organopoly(cyclosiloxanes) not always give soluble polymers and their yield is usually low [99-103]. Synthesized organobi- and -tricyclicsiloxane compounds were used in the polymerization reaction, which was performed in the presence of α,ω−tetramethylammonium

Organosilicon Copolymers with Monocyclic Fragments …

257

oxydimethylsiloxanolate (n = 11) and 0.1 N KOH alcohol solution in the temperature range of 50 - 200°C. It was found that the reaction proceeding at low temperature (<100°C) gives lowmolecular oligomers (ηspec=0.04). The reaction temperature increase over 140°C induces decomposition of the catalyst mentioned. That is why future studies of polymerization of organodi- and organotricyclosiloxanes were carried out in 0.1 N alcohol solution of potassium hydroxide. Di- and tricyclic compounds were polymerized with formation of low-molecular cyclolinear copolymers [103, 104]: Me2 Si O On Ph Ph

Ph

Cat

Ph O (SiMe2O)n

Ph

Ph

Ph

Ph

Me3SiO

OSiMe3

Me3SiO

OSiMe3

x

XXII Scheme 19

Ph

Ph

Me3SiO Me3SiO Ph

Ph

Me2 Ph O-(Si-O)n

Ph Cat OSiMe3

O-(Si-O)n Me2 Ph

OSiMe3 Ph

Ph

Ph O (SiMe2O)n

Ph Me3SiO

Ph OSiMe3 XXII

x

Scheme 20

Where: n = 1, 2. Synthesized regular copolymers represent light-yellow solids with ηspec=0.4-0.7, well soluble in va-rious organic solvents. It is found that the effect of increasing catalyst concentration (0.1–0.5 wt.% of initial compound) and reaction temperature on the molecular mass of low-molecular compounds obtained is negligible. Thermogravimetric analysis has indicated mass losses of copolymers at 260 - 270°C not exceeding 2 – 3%. At 300 – 350°C thermal degradation rate is considerably increased, and at 550°C mass losses are maximal. The mass loss is regularly increased with the length of dimethylsiloxane backbone, i.e. at transition from dimethylsiloxane to disiloxane bridge. Thus, synthesis of cyclolinear organosiloxane and carbosiloxane copolymers with monocyclic frag-ments in the backbone, obtained in HFC, hydride polyaddition and polymerization reactions, are considered in this review. The above-shown data on highmolecular polymers with regular dispo-sition of cyclic fragment in the backbone are mainly synthesized by HFC and hydride polyaddition reactions. As for polymerization of bicyclosiloxanes, they are almost useless for high polymer syn-thesis.

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INDEX A accumulation, 38 accuracy, 91, 93, 99, 123 acetic acid, 3 acetone, 48 acid, 61, 114, 118, 129, 138, 142, 150, 152, 159, 163, 169, 170, 192, 193, 194, 196, 202, 204, 249, 252 acidity, 56 acrylonitrile, 116, 144 activated carbon, 31, 39 activation, 11, 27, 82, 83, 84, 85, 167, 170, 203 activation energy, 27, 167, 203 active site, 94, 127, 144 additives, 47, 48, 50, 53, 56, 59, 60, 61, 62, 64, 65, 66, 104, 115, 116, 118, 119, 120 adhesion, 119, 123 adsorption, 29, 31, 35, 36, 37, 42, 43, 45, 114 affect, 55, 199, 235 age, 2, 91 ageing, 4, 5, 10, 11, 127, 146 agent, 92, 93, 107, 114, 115, 116, 118, 119, 124, 176, 179, 180, 198, 202, 205, 235 aggregates, 30, 33, 134, 230 aggregation, 30, 133 agriculture, vii, 2, 113, 124 albumin, 33, 36, 38, 42, 43, 45 alcohol, 122, 150, 155, 159, 204, 229, 230, 249, 253, 257 alcohols, 113, 114, 244 aldehydes, 114 alkylation, 56, 64 alternative, 57 alternatives, 174 aluminum, 116 amines, 145, 175, 221, 224, 236, 244 amino-groups, 45 ammonium, 225

amorphous polymers, 130, 163, 237, 246, 249 amplitude, 139 anger, 7 animals, 7, 38, 88, 102 anisotropy, 136 annealing, 177, 178 annihilation, 70 anomalous diffusion, 73, 74, 78 antagonism, 87 anther, 102 antibiotic, 36, 37, 38, 39 antioxidant, 53, 56, 64, 65 antioxidant additives, 65 antitumor, 10 applied research, 3 aqueous solutions, 36 argon, 31, 150, 194, 195, 224, 236, 249 argument, 77 aromatic hydrocarbons, 54, 55 artery, 30 assessment, 9, 151, 210, 211, 250 assimilation, 96 assumptions, 68, 70 asymmetry, 207, 208 atoms, 13, 14, 15, 16, 17, 18, 19, 20, 27, 81, 167, 170, 174, 175, 180, 185, 198, 205, 206, 207, 220, 221, 225, 226, 228, 235, 247 attention, 77, 127, 132, 188, 197, 223, 244 availability, 114

B barbiturates, 41, 43, 45 barriers, 83 basicity, 174, 175 behavior, 34, 42, 93, 188, 190, 229 bending, 115, 238, 239 benzene, 175, 188, 191, 192, 196, 202, 203, 204, 205, 206, 207, 218, 222, 225, 230, 231, 247

264

Index

bilirubin, 41, 43, 44, 45 biologically active compounds, 42 biotechnology, 42 birefringence, 185 birth, 98, 104, 106 blood, 30, 36, 39, 41, 42, 43, 44, 45 blood plasma, 39 blood supply, 30 bloodstream, 30, 31 body, 30 Boltzmann constant, 70 bonding, 115, 116, 119, 120, 167, 193 bonds, 13, 18, 19, 20, 33, 55, 138, 140, 141, 174, 185, 210, 211, 225, 226, 228, 229, 241 boric acid, 118 branching, 98, 100, 193, 198, 223, 229, 243, 244 breakdown, 239 breathing, 38 bromine, 55, 81, 82, 83, 84 buildings, 121 burning, 120, 121, 122 butadiene, 144, 146 butadiene-styrene, 146

C cadmium, 33 Canada, 6 cancer, 29, 30, 36, 39, 90, 92 carbon, 18, 19, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 41, 42, 43, 44, 45, 81, 82, 83, 121 carbon monoxide, 30 carbon nanotubes, 33 carbonization, 122 carcinogen, 103 carcinogenesis, 88 carcinoma, 89, 101, 102, 103 cardiac arrest, 38 carrier, 31, 39, 244 catalyst, 53, 54, 149, 152, 159, 168, 169, 170, 192, 193, 194, 197, 200, 201, 204, 251, 252, 257 catalytic activity, 197 catalytic system, 56, 113, 124, 149, 191, 198 catheter, 30 cation, 151 C-C, 24 cell, 42, 87, 92, 95, 98, 99, 103, 178, 183 cell cycle, 95 cellulose, 114 chain branching, 105, 206 chain molecules, 147 chain propagation, 104, 234 chain rigidity, 128, 164, 202, 233, 235

chain transfer, 217 chains conformation, 128 characteristic viscosity, 207, 227 chemical bonds, 13, 14, 19, 27 chemical kinetics, 3, 5, 87, 111 chemical properties, 36, 39, 119, 120, 122, 133, 149, 168, 192, 206, 217, 245 chemical reactions, 14, 27, 96, 97 chemotherapy, 10, 30, 90, 91, 92 China, 5, 6 chlorine, 220 chloroform, 207 chromatography, 43, 160, 241 chromium, 94, 99 classes, 59, 244 classification, 95 cleavage, 168 cleavages, 243 clinical oncology, 10 clinical trials, 30 cluster, 69 CMC, 62, 65, 116, 117, 119, 123, 124 coal, 42, 43, 168, 169, 200, 201 cobalt, 53 coherence, 238 cohesion, 120 coke, 115, 121, 122 colon, 90 combustibility, 120 combustion, 122 communication, 8 communism, 7 Communist Party, 2 community, 9, 94 compatibility, 48 competition, 105 compliance, 231 components, 14, 60, 61, 114, 115, 116, 122, 123, 128, 130, 142, 143, 169, 176, 183, 188, 202, 204, 205, 217, 230, 236, 247 composites, 43, 44, 45 composition, 31, 42, 59, 60, 61, 64, 65, 67, 71, 74, 123, 156, 173, 190, 198, 226, 230, 243, 253 compounds, 2, 13, 53, 54, 56, 59, 61, 65, 114, 149, 151, 152, 154, 157, 159, 167, 173, 182, 194, 197, 198, 205, 219, 221, 230, 234, 235, 240, 244, 247, 248, 249, 250, 251, 252, 253, 256, 257 computation, 20 concentration, 30, 36, 38, 39, 43, 44, 50, 60, 61, 62, 64, 65, 94, 99, 100, 104, 105, 108, 109, 110, 111, 116, 118, 119, 128, 130, 140, 141, 142, 145, 146, 156, 157, 159, 160, 161, 162, 164, 169, 192, 193, 230, 234, 246, 249, 254, 257

Index conception, 68 conceptualization, 233 concrete, 119, 120 condensation, 31, 32, 167, 168, 169, 200, 201, 219, 221, 246, 248 conduction, 120 conductivity, 120 conductor, 68 configuration, 14, 128, 174, 175, 176, 183, 184, 185, 186, 201, 235 conflict, 20 connectivity, 76, 77 consciousness, 6 constitution, 74 construction, 4, 119, 120 consumption, 65, 121 contamination, 122 control, 89, 95, 100, 105 conversion, 153, 159, 160, 169, 219, 220, 221, 225, 240, 241, 245, 247 cooling, 31, 32, 39, 42, 177, 178, 186 copolymers, 149, 150, 152, 153, 154, 155, 156, 157, 158, 159, 160, 161, 162, 163, 164, 169, 170, 171, 172, 183, 186, 190, 191, 194, 195, 196, 197, 199, 200, 202, 203, 204, 205, 218, 221, 222, 223, 224, 225, 227, 229, 230, 231, 232, 233, 234, 235, 245, 246, 247, 248, 249, 251, 252, 253, 254, 255, 256, 257, 258 copper, 94, 114 correlation, 33, 54, 136, 138, 140, 141, 143, 174, 178, 241 corrosion, 116 costs, 116 cotton, 120 coupling, 42 covalent bond, 128 coverage, 117 covering, 121, 122 creativity, 3 critical value, 104 crops, 115 cross-linked polymers, 151, 217, 251 cross-linking reaction, 196, 231 crystal polymers, 191 crystallinity, 68, 74, 173, 178 crystallites, 51, 52 crystallization, 47, 49, 52, 178, 186, 238 crystals, 50, 51 culture, 95, 111 cyanocobalamin, 43 cycles, 151, 167, 169, 251

265

D danger, 122 database, 88, 92, 93 death, 2, 38, 93, 121 decomposition, 48, 138, 193, 235, 239, 240, 257 decomposition temperature, 235 defects, 50, 74 deformability, 207 deformation, 118, 206 degradation, 73, 78, 157, 162, 164, 178, 179, 180, 190, 195, 204, 206, 230, 231, 241, 243, 248, 254 degradation process, 157, 162, 204, 248, 254 degree of crystallinity, 185 dehydrocondensation, 169, 170, 171, 202, 203 demand, 59 density, 14, 39, 50, 68, 74, 120, 140, 141 depolymerization, 191, 231 deposition, 60 derivatives, 75, 172, 174, 175, 176, 183, 184, 244 desorption, 29, 30, 36, 37, 39 destruction, 10, 48, 98, 118, 144, 145, 172 destruction processes, 144, 145 detachment, 193, 235 detergents, 122, 123, 133, 137 deviation, 190 dielectric constant, 224 dienes, 53, 54 differential scanning, 198 differential scanning calorimetry, 198 diffraction, 178, 179, 182, 185, 188, 198, 232, 235, 236, 238, 246, 249 diffusion, 67, 68, 69, 71, 73, 75, 76, 77, 78, 116, 136 diffusion process, 68, 71, 76 diffusivity, 68, 69, 71 dihydroxy-containing oligomers, 247 dimethylformamide, 132 direct measure, 13 disclosure, 159, 168 disordered systems, 135 dispersion, 64, 65, 116, 122, 235, 239 dispersity, 30 displacement, 50, 75, 117 disposition, 150, 154, 155, 156, 157, 158, 188, 205, 218, 220, 222, 223, 224, 225, 231, 233, 235, 253, 254, 255, 256 dissociation, 20 distilled water, 43 distribution, 33, 127, 144, 174, 179, 180, 240, 244 division, 75, 95, 97 DMF, 57, 58 DNA, 95 doctors, 5

266

Index

dominance, 186 donors, 10 dosage, 65, 123 double bonds, 54, 55, 56 double logarithmic coordinates, 188 drug carriers, 36 drug delivery, 30, 39 drugs, 29, 30, 39 drying, 119, 123 DSC, 173, 174, 176, 177, 178, 179, 182, 185, 186, 198, 234, 236 DTA curve, 191 durability, 50, 56 duration, 88, 91, 240

E Egypt, 1, 86 elasticity, 70, 74, 119, 206 elasticity modulus, 70, 74 election, 4 electron microscopy, 33 electronic structure, 79, 80 electrons, 13, 14, 15, 16, 17, 19, 20, 114, 133 embryo, 104 emulsions, 65 endurance, 38 energy consumption, 113 energy parameters, 14 England, 2 entropy, 187 environment, 54, 58, 67, 68, 71, 96, 97, 113 enzymes, 42 EPR-spectroscopy, 127, 128, 132, 133, 144, 145 equality, 98, 100, 102, 230 equilibrium, 107, 108, 109, 111, 172, 184, 187, 188, 190 equipment, 116 erythrocyte, 41 estimating, 14, 20, 87, 207, 221, 226 Estonia, 3 ethanol, 207 ethylene, 145, 191, 193, 194, 204 Euclidean space, 74 Europe, 124 evacuation, 121 evaporation, 31, 39 evidence, 94 experimental condition, 221 exploitation, 119 expression, 102, 103 extinction, 109 extraction, 188

extrapolation, 208, 210, 227

F fabric, 120 family, 109, 110 fibers, 48, 49, 50, 51, 52 fibrillation, 49, 50 filament, 34 filled polymers, 10 film formation, 206 films, 60, 74, 123, 124, 205, 207, 230 filtration, 116, 117, 230 financing, 4 fission, 95, 183 fixation, 123 flame, 120 flammability, 4, 5 flexibility, 71, 188, 199, 201, 207, 208, 209, 211, 226 flexible-chain polymers, 173 fluid, 37 fluorine, 114 focusing, 38, 50 food, 2, 4 forecasting, 5 foreign language, 5 formaldehyde, 115 fractal dimension, 69, 70, 74 fractal objects, 75 framing, 170, 179, 191, 193, 206, 222, 223, 231, 235, 244, 247, 249 France, 3 free radicals, 3, 114 free rotation, 209, 211, 226, 228 free volume, 69, 70 friction, 59, 61 friends, 4, 9 fuel, 3 functionalization, 55, 56 fungus, 115 furan, 169

G gel, 118, 151, 160, 172, 198, 203, 207, 225, 251 gel formation, 225 gel permeation chromatography, 172, 203 generation, 5, 10, 122 geometrical parameters, 80, 88 Georgia, 149, 164, 165, 167, 215, 216, 217, 258, 261, 262 Germany, vii, 43

Index gland, 89 glass transition, 157, 162, 173, 178, 186, 190, 196, 206, 235, 246 glass transition temperature, 157, 162, 196, 206, 235, 246 glycol, 141 GPC, 172, 198, 207 graduate students, 5 graph, 105 gravimetric analysis, 204 gravity, 236 groups, 38, 45, 48, 74, 83, 106, 114, 135, 136, 138, 139, 140, 141, 143, 144, 149, 151, 152, 153, 154, 156, 161, 162, 167, 168, 170, 179, 180, 181, 183, 186, 187, 191, 192, 193, 194, 195, 196, 198, 199, 200, 201, 205, 206, 210, 217, 218, 220, 221, 222, 223, 225, 226, 229, 230, 231, 232, 233, 234, 237, 244, 247, 249, 250, 252, 254 growth, 62, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 115, 118, 123, 138, 194, 228, 239 growth factor, 94 growth rate, 90, 101, 103, 108, 194

H halogen, 19, 79, 80, 82 halos, 198, 232, 235 HDPE, 67, 68, 69, 70, 71, 74, 75, 76, 77, 78 HDPE+Z, 67, 68, 70, 71, 74, 75, 76, 77, 78 health, 7 heat, 119, 121, 122, 182, 185, 187, 200, 206, 236, 238 heating, 52, 74, 121, 150, 151, 152, 159, 162, 169, 177, 178, 193, 195, 223, 249, 250, 252 heating rate, 74, 162, 195, 223 height, 188, 237, 238 helium, 74, 75, 76, 77 heme, 41, 43, 44, 45 hemoglobin, 43, 45 heptane, 53 heterofunctional condensation, 168, 169, 171 heterogeneity, 35, 39, 117, 143 hexane, 193 high density polyethylene, 67, 73, 74 high school, 52 high-molecular compounds, 210 HIV, 79 HIV-1, 79 homopolycondensation, 256 homopolymers, 186 horizontal microscope, 122 human immunodeficiency virus, 79

267

hybridization, 13, 14, 18, 19, 20, 21, 22, 23 hydrides, 20 hydrocarbons, 3, 53, 150, 244, 250 hydrogen, 3, 18, 19, 45, 57, 114, 138, 141, 143, 144, 169, 170, 171, 172, 195, 196, 204, 219, 220, 221, 231, 233, 245, 247 hydrogen atoms, 141 hydrogen bonds, 45, 138, 141, 144 hydrogen chloride, 172, 204, 219, 220, 221, 233, 245, 247 hydrogen peroxide, 114 hydrolysis, 151, 175, 217, 218, 229, 234, 250 hydrosilylation, 191, 192, 197, 205, 206 hydroxide, 202, 203, 257 hydroxyl, 141, 218, 221 hydroxyl groups, 141, 218, 221 hypothesis, 92

I ideas, vii, 3, 6, 8, 9, 11, 87 identification, 91, 100, 102, 144 identity, 241 image analysis, 33 immobilization, 42 implementation, 3 impregnation, 120 in vitro, 79 inclusion, 84, 183, 239 India, 5 induction, 10, 60, 104, 169 induction period, 60, 169 industry, 4, 59, 113, 114, 116, 117, 119 inefficiency, 92 influence, 2, 20, 44, 47, 48, 61, 66, 69, 73, 74, 78, 87, 88, 91, 100, 106, 107, 108, 117, 119, 121, 122, 137, 138, 140, 164, 179, 183, 184, 188, 225, 226, 230, 247 inhibition, 90, 94, 96, 98, 100, 104 inhibitor, 99, 104, 105, 116 initial reagents, 150, 198, 221, 249 initiation, 94, 193 injections, 38 inoculation, 95 inoculum, 91, 103 instability, 167 intensity, 42, 75, 88, 128, 175, 184, 185, 198, 230, 238, 239 interaction, 14, 19, 20, 45, 54, 55, 57, 58, 65, 69, 114, 118, 128, 133, 135, 136, 142, 168, 172, 175, 184, 208, 210 interactions, 45, 54, 84, 96, 137, 207

268

Index

interest, 10, 14, 114, 132, 133, 151, 173, 188, 191, 199, 224, 250 interface, 47, 117, 135, 136, 137, 142 interfacial layer, 10 intermolecular interactions, 167, 179, 183, 200, 239 interpretation, 88 interval, 55, 62, 65, 68, 74, 95 inversion, 174, 175, 176, 183, 184, 185 ionization, 81, 82, 83, 138 ions, 94, 95, 114, 116, 133, 135, 139, 140, 174, 225 IR spectra, 151, 159, 250 iron, 10, 29, 30, 31, 32, 33, 34, 39, 41, 42, 43, 44, 45 IR-spectra, 54, 168 IR-spectroscopy, 145, 151, 250 isobutylene, 55, 56, 61 isolation, 98, 230 isomers, 5, 151, 152, 155, 167, 170, 173, 176, 182, 183, 184, 185, 198, 204, 221, 225, 228, 235, 250, 251, 253 isoprene, 53

J Japan, 5, 6, 65, 212, 215

K ketones, 114 kinetic constants, 96 kinetic equations, 87, 97 kinetic model, 89, 103 kinetic parameters, 82 kinetic research, 79, 80 kinetic studies, 89 kinetics, 3, 10, 14, 36, 39, 87, 88, 89, 90, 93, 94, 98, 103 knowledge, vii, 1, 59, 179, 235 KOH, 170, 171, 257

L laws, 85 lead, 30, 88, 118, 123, 133, 140, 218 liberation, 171, 196, 219, 220, 231 LIFE, 8 lifespan, 10 ligands, 42, 113 light scattering, 171, 207, 211, 230 linear dependence, 34, 89 linear polymers, 191 links, 153, 253 lipids, 10 liquid chromatography, 159, 234

liquid phase, 3, 85 liquids, 3, 67, 115, 117, 150, 164, 250 local mobility, 133, 136, 140, 142, 143, 144 local order, 70 localization, 67, 69, 71, 121, 136, 142 location, 61, 205, 220, 235 low temperatures, 235 LTD, 72 lubricants, 59, 65 lymph, 89, 102

M macromolecular coil, 75, 225, 227 macromolecules, 50, 55, 56, 127, 128, 129, 130, 131, 132, 133, 135, 136, 138, 140, 145, 147, 167, 183, 188, 190, 200, 207, 210, 211, 225, 227, 228, 229, 230, 233, 235, 236 magnesium, 94 magnet, 36 magnetic field, 30, 36, 42 magnetic moment, 30, 42 magnetic particles, 30, 31, 36, 42 magnetic properties, 30, 34, 39, 42 magnetic resonance, 148 magnetization, 29, 30, 34, 42, 43 malignant tumors, 88 management, 7 manufacturing, 5, 30, 31 mass, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 67, 68, 73, 74, 76, 77, 78, 88, 90, 92, 100, 115, 117, 118, 119, 120, 121, 122, 129, 132, 142, 143, 152, 153, 155, 157, 162, 164, 172, 181, 186, 190, 195, 196, 204, 205, 211, 221, 223, 230, 231, 241, 244, 246, 248, 251, 252, 253, 254, 256, 257 mass loss, 73, 76, 78, 121, 157, 162, 164, 172, 190, 195, 196, 204, 223, 231, 246, 248, 251, 254, 257 mass spectrometry, 241 material surface, 121 matrix, 96 maximum sorption, 43 measurement, 38, 60, 128, 230 mechanical properties, 207 mechanical testing, 74 median, 67, 68, 71 medication, 7 melanoma, 89 melt, 179, 181, 185, 186, 199, 234, 235 melting, 70, 74, 173, 178, 185, 186, 239 melting temperature, 70, 74 membranes, 10, 136 memory, 6, 8, 9, 10, 79 Mendeleev, 84

Index metals, 116, 149 metastasis, 91 methanol, 129, 132, 188, 202, 225, 245 methyl groups, 81, 182, 185, 186, 193, 206, 232 mice, 7, 38 microheterogeneous system, 11 microscope, 32, 48, 182, 185, 230 microspheres, 33, 42 microstructure, 47, 244 microvoid, 69, 70 migraines, 79 mitosis, 95 mixing, 18, 19, 20, 37, 42 mobile phone, 7 mobility, 50, 117, 133, 136, 137, 138, 140, 141, 143, 144, 145, 186 mode, 53, 67 model system, 36 modeling, 211 models, 80, 87, 88, 89, 93, 95, 100, 101, 104, 111, 180, 188, 237 mole, 54, 55, 56, 132, 139, 140, 192, 193 molecular dynamics, 127, 133, 134, 135, 141, 144 molecular mass, 41, 43, 44, 45, 129, 135, 137, 155, 160, 164, 181, 186, 187, 188, 192, 193, 197, 198, 199, 202, 206, 208, 209, 210, 211, 221, 224, 226, 227, 229, 230, 233, 235, 248, 253, 257 molecular mobility, 135, 142, 144 molecular structure, 13, 14, 196 molecular weight, 41, 42, 43, 44, 45, 48, 53, 54, 55, 58, 68, 74, 160, 239 molecules, 10, 20, 24, 36, 44, 52, 56, 69, 76, 77, 128, 133, 136, 137, 141, 142, 143, 144, 176, 199, 208, 210, 211, 241 monograph, 87, 127, 168, 211 monomers, 149, 173, 174, 175, 183, 184, 185, 191, 193, 205, 206 mortality, 97, 109 Moscow, 1, 2, 3, 4, 5, 6, 7, 9, 10, 13, 29, 39, 40, 41, 46, 53, 72, 78, 79, 87, 111, 113, 125, 127, 146, 147, 149, 165, 167, 211, 214, 217, 258, 259 motion, 138 myoglobin, 44

N nanocomposites, 10 natural sciences, vii necrosis, 10 needs, 7, 30 negative emotions, 7 Netherlands, 6, 27 network, 206, 223, 244

269

neutrons, 132 nickel, 94, 95, 99 nitrogen, 10, 18, 19, 20, 57, 61, 85, 224 nitrogen oxides, 10, 20 nitroxyl radicals, 144, 145, 146 NMR, 54, 151, 152, 154, 156, 159, 161, 172, 173, 174, 175, 176, 183, 184, 185, 192, 193, 194, 198, 200, 201, 205, 221, 222, 234, 241, 248, 250, 251, 253, 254 N-N, 22, 24, 26 Nobel Prize, vii nodes, 89, 109 nuclei, 172 nucleus, 14, 135, 142

O objective criteria, 87, 103 obligate, 231 observations, 100, 185 octane, 55, 56 OH-groups, 45 oil, 3, 59, 60, 61, 64, 65, 115, 116, 117, 118, 120, 122, 123, 136 oils, 53, 59, 65, 66, 117 oligomeric structures, 222 oligomerization, 53, 54, 184 oligomers, 55, 56, 58, 59, 61, 167, 168, 169, 171, 184, 191, 200, 201, 202, 203, 204, 206, 229, 240, 242, 247, 248, 257 oligopiperylene, 55, 56, 58, 59, 60, 63, 65 optical density, 36, 195 optimization, 31, 80, 101, 103 organic compounds, 4, 11, 65, 113, 114, 196, 230, 244 organic polymers, 235 organic solvents, 153, 155, 159, 160, 169, 170, 183, 192, 194, 202, 204, 221, 223, 225, 234, 248, 252, 253, 257 organism, 30, 38, 93, 95, 100, 108, 133 organization, 127, 133, 134, 135, 136, 137, 200 organocyclosiloxanes, 149, 167, 168, 169, 173, 202, 206, 207, 218, 225, 231, 256 oxidation, 3, 4, 10, 11, 33, 61, 113, 114, 115, 144, 145, 194 oxidation rate, 114 oxidative destruction, 127, 145, 146 oxides, 30, 42, 43, 167 oxygen, 56, 75, 82, 84, 85, 113, 114, 120, 121, 124, 149, 167, 180, 200

270

Index

P PAA, 134, 136, 137, 141 packaging, 140 pain, 6 paints, 119 parameter, 13, 14, 18, 19, 20, 24, 26, 55, 56, 73, 89, 94, 102, 106, 109, 128, 129, 130, 132, 136, 137, 190, 207, 208, 209, 210, 211, 227, 229 parameter estimation, 227 particles, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 42, 43, 44, 77, 116, 122, 134 pathogens, 30, 39 permeability, 118, 190 permeation, 198 peroxide, 10, 144, 145 peroxide radical, 144, 145 perspective, 5, 14, 87, 113, 145 pH, 43, 44, 45, 138, 139, 140 pharmacology, 11 phase diagram, 180, 186 phase transitions, 177, 180, 181 phenol, 5, 56, 58, 60, 61, 64, 115 phospholipids, 136 physical chemistry, 128, 146 physical-mechanical properties, 120 physics, vii, 1, 3, 27, 127, 146, 147 pine, 121, 122 piperylene, 53, 54, 59, 60, 61, 62, 64, 65 plants, 4, 115 plasma, 39, 43, 44, 45 plasma proteins, 43, 44, 45 plasticity, 119 plasticization, 47, 50 platinum, 152, 159, 163, 169, 170, 192, 193, 194, 196, 197, 204, 252 poison, 95 polar groups, 183 polarity, 174 polarization, 182, 185 police, 7 polybutadiene, 144, 145 polycarbonate, 74 polycondensation, 154, 169, 218, 219, 220, 222, 253 polydimethylsiloxane, 167, 222 polydispersity, 207 polyethylenes, 67, 71 polymer chains, 128, 137, 138, 144, 145, 147 polymer destruction, 144 polymer materials, 10, 120, 133, 144 polymer molecule, 208 polymer networks, 206 polymer oxidation, 144

polymer properties, 133 polymer structure, 69, 74, 76, 77, 151, 239, 241, 251 polymer systems, 127, 133 polymeric chains, 180, 188 polymeric macromolecules, 69 polymeric materials, 5, 47, 74, 75 polymeric melt, 75 polymeric products, 4, 5, 221 polymerization, 65, 128, 129, 135, 151, 154, 159, 167, 169, 181, 184, 187, 198, 217, 220, 239, 251, 253, 256, 257 polymers, 2, 4, 5, 10, 42, 47, 48, 51, 53, 67, 71, 73, 117, 127, 128, 129, 130, 134, 144, 145, 146, 147, 149, 150, 151, 152, 159, 164, 167, 170, 172, 173, 174, 179, 180, 181, 182, 183, 184, 185, 186, 187, 188, 190, 191, 192, 193, 195, 196, 197, 198, 199, 201, 205, 206, 209, 217, 218, 223, 226, 230, 231, 233, 235, 236, 239, 240, 249, 250, 251, 256, 257 polyolefins, 65 polyphosphates, 122 polypropylene, 146 polystyrene, 144 polyurethane, 3 poor, 4 population, 87, 88, 94, 95, 96, 97, 98, 99, 100, 101, 102, 105, 107, 109 population growth, 87, 95, 97, 99, 100 positrons, 70 potassium, 116, 169, 203, 257 power, 2, 64, 71, 83, 98 precipitation, 60, 187, 202, 204, 230, 236 prediction, 19, 68 preparation, 31, 37, 38, 92, 93, 100, 109 pressure, 50, 59, 68, 74, 117 prevention, 92 prices, 123 primary products, 114, 243 primary tumor, 93 principle, 2, 14, 18, 19 probability, 2, 92, 93 probe, 129, 130, 135, 136, 137, 142, 143, 144 production, 3, 4, 5, 29, 31, 68, 74, 114, 115, 116, 117, 118, 120, 244 productivity, 113 program, 241 proliferation, 105 promoter, 104 propagation, 106 proportionality, 88 propylene, 3, 145 prosperity, vii proteins, 42, 43, 44, 45 protons, 54, 156, 161, 194, 205, 248, 254

Index pure water, 120 purification, 41, 42, 224, 230 PVP, 129, 130, 132 pyrolysis, 196, 230, 231, 239, 240, 241, 242, 243, 247

Q quantitative estimation, 190 quantum-chemical calculations, 82

R radical mechanism, 10, 195, 231 radical reactions, 5 radius, 14, 18, 20, 24, 26 range, 34, 54, 152, 157, 162, 163, 164, 172, 173, 175, 177, 178, 179, 180, 181, 185, 186, 187, 188, 190, 192, 193, 194, 195, 196, 199, 204, 205, 207, 223, 224, 229, 230, 235, 236, 238, 239, 240, 244, 248, 252, 254, 257 raw materials, 114, 115, 119, 121, 124 reactant, 57 reaction center, 175 reaction order, 203 reaction rate, 154, 160, 170, 203, 253 reaction rate constants, 154, 160, 170, 203, 253 reaction temperature, 150, 156, 174, 198, 254, 257 reaction zone, 57 reactive groups, 221 reagents, 104, 114, 115, 116, 120, 121, 122, 123, 124, 202, 206, 247 reasoning, 4 recall, 6 reception, 48, 79, 80, 84, 102 recovery, 92, 117 rectification, 151, 204, 250 reduction, 5, 10, 30, 50, 71, 81, 109, 114, 123 reflexes, 174, 175, 176, 178, 182, 183, 184, 194, 198, 205, 236 refraction index, 245 regression, 93 regulation, 105, 167, 178, 234, 235 relationship, 70, 71, 74 relationships, 71 relaxation, 2 rent, 198, 227 replacement, 69, 79, 80, 81, 82, 83, 84 reproduction, 84, 95, 96, 97, 98, 105 resins, 239 resistance, 41, 43, 44, 45, 91, 92, 93, 120, 164, 194, 206 retention, 240, 241

271

rhodium, 159 rice, 82, 83, 115, 118, 119, 120, 121, 122, 123 risk, 120, 121 room temperature, 36, 37, 43, 114, 178, 192, 202, 204, 218, 220 rotational mobility, 145 Royal Society, 146 rubber, 53 rubbers, 244 Russia, 1, 9, 13, 29, 41, 43, 47, 53, 65, 67, 79, 87, 113, 124, 125, 127, 149, 167, 217

S salts, 94, 99, 115, 116 sample, 54, 67, 68, 71, 73, 74, 78, 122, 144, 145, 146, 178, 187, 190 saturation, 30, 34, 36, 37, 39, 42, 178 sawdust, 120 scaling, 147 scanning calorimetry, 176 scattering, 128, 130, 132, 198, 208, 230 search, 88, 102, 113 second virial coefficient, 208 sediment, 37 sedimentation, 36, 37 seed, 123, 124 selecting, 129 selectivity, 79, 84, 113, 114, 244 self, 133, 196, 200, 201 self-organization, 200, 201 sensitivity, 90, 91, 92, 93, 95, 108, 109 separation, 35, 42, 95, 217, 238, 244, 245 series, 54, 151, 167, 174, 183, 217, 241, 242, 244, 250 serum, 36, 104 shape, 33, 198, 228, 238 shear, 118 shock, 2 side effects, 7 sign, 76 signals, 33, 54, 55 silane, 168, 217 silica, 41, 42, 43, 44, 45 silicon, 42, 167, 169, 170, 174, 185, 190, 198, 202, 205, 206, 207, 210, 218, 219, 220, 221, 225, 231, 232, 247 silver, 94 simulation, 207, 225 sites, 128, 130 skin, 88 smoke, 120, 121 sodium, 43, 116, 122, 123, 129, 134, 168, 169

272

Index

sodium hydroxide, 168 software, 33, 80 solid phase, 116 solid polymers, 130, 132 solid state, 127, 128, 130, 132 solubility, 48, 58, 115, 133, 193 solvents, 53, 56, 57, 61, 64, 65, 74, 129, 130, 132, 168, 169, 175, 176, 196, 201, 208, 227, 233 sorption, 29, 30, 36, 37, 39, 41, 42, 43, 44, 45 South Korea, 5 Soviet Union, 2 specific surface, 31, 32, 36 specificity, 149, 191 spectra analysis, 136 spectral dimension, 69 spectrophotometry, 36 spectroscopy, 14, 27, 33, 43, 54, 127, 133, 172, 173, 176, 193, 198, 241 spectrum, 33, 35, 54, 83, 113, 138, 140, 141, 142, 143, 145, 146, 156, 161, 185, 192, 194, 230, 248, 254 speech, 10 speed, 8, 82, 83, 84 spin, 127, 128, 129, 130, 132, 133, 135, 136, 137, 138, 139, 140, 141, 142, 143, 144, 145 stability, 5, 39, 47, 48, 60, 62, 67, 68, 70, 71, 149, 157, 162, 164, 172, 175, 201, 217, 231, 244, 246, 247, 248, 254 stabilization, 4, 11, 62, 127, 146, 178, 186 stabilizers, 4, 5 stages, 30, 83, 87, 95, 97, 107, 144, 156, 169, 254 starch, 114, 115, 116, 119, 120, 121, 122 statistics, 121, 147 steel, 59 stereospecificity, 175 storage, 5 strain, 68, 74, 91, 102 strength, 13, 67, 115, 119, 120, 123, 206, 207 stress, 67, 68, 70, 71, 74, 118, 190 stroma, 92 strong interaction, 235 structural changes, 67, 70, 71 structuring, 144, 159, 230 students, vii, 5, 6 styrene, 129, 144 substitution, 101, 102, 103, 116, 123, 186, 200, 206, 232, 247 substrates, 95, 96, 97, 98 sulfur, 3, 10, 53, 54, 55, 56, 57, 58, 59, 61, 65, 81, 82 superimposition, 30 supervisor, 6 suppression, 38, 235 surface modification, 41

surface tension, 32 survival, 93 susceptibility, 30, 42 suspensions, 30, 33, 38, 42 Sweden, vii, 6 symbols, 242 symmetry, 33, 136, 190 syndrome, 43 synthesis, 3, 10, 54, 55, 80, 95, 114, 149, 150, 159, 167, 168, 169, 175, 183, 184, 191, 197, 206, 217, 218, 221, 225, 240, 246, 257 synthesized copolymers, 152, 155, 160, 162, 170, 224, 245, 248, 251, 253 systems, 6, 14, 84, 96, 97, 100, 127, 130, 136, 142, 149, 157, 159, 162, 163, 171, 196, 201, 204, 232, 254

T tacticity, 176, 178, 179, 184, 185, 186, 233, 237, 238, 239 teaching, 5 technology, 4, 29, 31, 39, 42, 52, 66 telephone, 8 temperature, 31, 32, 36, 43, 48, 50, 51, 53, 55, 56, 68, 73, 74, 76, 78, 80, 82, 116, 121, 122, 130, 152, 153, 157, 159, 160, 161, 162, 163, 168, 169, 170, 172, 173, 177, 178, 179, 180, 181, 182, 183, 185, 186, 187, 188, 192, 193, 194, 195, 197, 199, 200, 203, 206, 207, 222, 223, 224, 227, 228, 230, 234, 235, 236, 238, 239, 240, 241, 244, 248, 252, 254, 257 temperature dependence, 178, 188, 238 tension, 68, 74 tetrahydrofuran, 150, 163, 192, 194, 204, 249 TGA, 73, 76, 77, 78, 152, 251 theory, 3, 70, 75, 87, 101, 103, 104, 128, 130 therapy, 91, 92, 93, 107 thermal analysis, 236 thermal degradation, 73, 195, 230, 231, 239, 257 thermal oxidative degradation, 164, 193 thermal properties, 73 thermal stability, 149, 195, 205, 206, 233, 235, 236, 244 thermodynamics, 83, 111 thermogravimetric analysis, 73 thermostability, 73, 74, 75 thin films, 201 thinking, 4 thrombosis, 38 thyroid, 79 thyroid gland, 79

Index time, 1, 2, 3, 4, 5, 6, 7, 20, 29, 30, 53, 67, 68, 75, 76, 82, 87, 89, 90, 91, 93, 95, 99, 100, 103, 106, 119, 120, 122, 127, 136, 138, 140, 141, 143, 159, 160, 169, 195, 205, 219, 227, 229, 240, 241 tissue, 30, 88 toluene, 54, 150, 153, 155, 159, 160, 163, 168, 169, 171, 175, 188, 193, 194, 197, 200, 202, 204, 207, 208, 218, 220, 221, 223, 227, 228, 229, 234, 238, 245, 247, 249, 250, 252, 253, 256 topology, 76 toxic effect, 30 toxic products, 121 toxic substances, 133 toxicity, 29, 38, 39, 41, 116, 120, 121, 122 trajectory, 76, 77 transformation, 174, 247 transition, 82, 100, 116, 137, 138, 140, 141, 151, 157, 169, 173, 176, 178, 181, 183, 185, 186, 190, 226, 229, 231, 233, 251, 254, 257 transition temperature, 190 transitions, 100, 114, 178, 179, 180, 184, 185, 186, 198, 225, 229, 236, 238 translation, 178 transplantation, 104 transport, 29, 30, 39, 67, 68, 69, 71, 76, 77, 133 transport processes, 67, 69, 71, 76 tumor, 5, 7, 29, 30, 39, 87, 88, 89, 90, 91, 92, 93, 100, 103, 104, 105, 111 tumor cells, 92, 93 tumor growth, 87, 88, 89, 91, 92, 93, 100, 103, 104, 105 tumors, 88, 89, 90, 91, 92, 93, 95, 100, 103, 104, 105, 111

U Ukraine, 72 ultrasound, 33, 36, 37, 42 uniform, 36 universities, 8 USSR, vii, 1, 2, 3, 4, 5, 6, 7, 9, 40, 46, 87, 124, 125, 164, 165, 211, 258, 259, 261, 262 uterus, 102 UV, 36, 43

109, 111, 122, 129, 130, 132, 135, 136, 138, 141, 150, 153, 156, 167, 172, 181, 186, 187, 190, 198, 203, 205, 206, 207, 208, 210, 211, 219, 221, 222, 225, 226, 228, 233, 238, 241, 248, 250, 252, 254 vapor, 32 variable, 88, 100 variables, 88 variation, 71, 75, 149, 151, 169, 172, 180, 181, 201, 206, 217, 237, 238, 246, 250 vector, 96 viscosity, 60, 115, 117, 118, 123, 150, 151, 160, 193, 194, 195, 197, 205, 222, 224, 245, 249, 250, 251 vitamin E, 5 vitrification temperature, 130 voting, 4

W war, 3 water, 33, 36, 37, 43, 65, 69, 80, 114, 115, 116, 117, 118, 120, 122, 123, 132, 133, 136, 138, 139, 140, 141, 143 water-soluble polymers, 116, 120 wealth, vii wear, 53 weight ratio, 118 Western Europe, 5, 6 wood, 120, 121, 122 words, 1, 8, 13, 130, 140 work, 2, 3, 5, 6, 7, 8, 9, 10, 11, 13, 34, 56, 87, 88, 91, 100, 145, 168, 188, 197, 210, 221, 227, 228 workers, 5, 7, 178

X X-ray diffraction, 157, 163, 171, 173, 180, 201, 232, 241, 249, 254 X-ray diffraction data, 180

Y yeast, 94, 95, 99 yield, 54, 58, 153, 171, 185, 204, 221, 222, 236, 245, 246, 252, 256

V vacuum, 221, 224 valence, 14, 18, 19, 20, 211, 226, 228, 235, 247 values, 13, 14, 18, 19, 20, 43, 55, 58, 59, 62, 65, 70, 74, 76, 77, 85, 90, 98, 99, 100, 101, 103, 104,

273

Z zinc, 59