Comb-Shaped Polymers and Liquid Crystals

424 Pages·1987·9.625 MB·English

by  N. A. Platé, V. P. Shibaev (auth.)

Comb-Shaped
Polymers and
Liquid Crystals
SPECIALTY POLYMERS
Series Editor
J. M. G. Cowie, University oj Stirling, Stirling, Scot/and
ALTERNATING COPOLYMERS
Edited by J. M. G. Cowie
COMB-SHAPED POLYMERS AND LIQUID CRYSTALS
N. A. Plate and V. P. Shibaev
Comb-Shaped
Polymers and
Liquid Crystals
N. A. Plate
and
V. P. Shibaev
Moscow State University
Moscow, USSR
Translated from Russian by
S. L. Schnur
Translation Edited by
J. M. G. Cowie
University of Stirling
Stirling, Scotland
Plenum Press • New York and London
Library of Congress Cataloging in Publication Data
Plate, Nikolai Al'fredovich.
Comb-shaped polymers and liquid crystals.
(Specialty polymers)
Translation of: Grebneobraznye polimery i zhidkie kristally.
Bibliography: p.
Includes index.
1. Polymer liquid crystals. I. Shibaev, V. P. (Valerii Petrovich) II. Title. III. Series.
QD923.P5613 1987 547.7 87-18518
ISBN-13: 978-1-4612-9082-7 e-ISBN: 978-1-4613-1951-1
001: 10.1007/978-1-4613-1951-1
© 1987 Plenum Press, New York
Softcover reprint ofthe hardcover 1 st Edition 1987
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All rights reserved
No part of this book may be reproduced, stored in a retrieval system, or transmitted
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Preface
to the American Edition
We are pleased that our modest work, published some time
ago in Russian in Moscow* and which attracted the attention
of polymer specialists,t will now be available to the EngJish
speaking audience of scientists - chemists, physicists, and
technologists engaged in creating new types of polymer materi
als for modern technology and working on the fundamental prob
lems of the solid-state physics and structure of polymers -
due to the initiative of Plenum Press.
In polymer science, the 1980s were marked by the birth
of a new field and a new scientific trend related to the dis
covery and study of a previously unknown class of polymers
thermotropic liquid-crystalline polymers - and the further
development of the fundamental theoretical concepts of the
liquid-crystalline (mesomorphic) state of macromolecular com
pounds. This state is a phase state in thermodynamic equi
librium characterized by the anisotropy of the structure and
properties as a result of one-dimensional or two-dimensional
ordering. Such systems have an ordered but simultaneously
labile structure which can easily be altered by mechanical,
electrical, or magnetic fields; the polymer system then
acquires unique physical and optical properties. These prop
erties, which are acquired in the liquid-crvstalline state,
are then fixed in the solid at the operating temperatures.
*N. A. Plate and V. P. Shibaev. Comb-Shaped Polymers and Li
quid Crystals [in RussianJ. Khimiya, Moscow (1980).
tSee the review of this book by H. Mark in J. Polym. Sci.
Polym. Lett. Ed., 20, 139 (L982).
v
vi PREFACE
This feature of liquid-crystalline polymers opens up broad
possibilities for the preparation of new polymeric glasses,
films, fibers, and coatings.
The class of branched macromolecules in the comb state,
i.e., containing long aliphatic branches in each monomeric
unit, is one of the typical representatives of such polymers
which tend toward self-organization. Addition of mesogenic
groups to the side branches of comb-shaped polymers can re
sult in the formation of any of the known low-molecular
weight liquid crystals of the mesophase type: nematic, smec
tic, or cholesteric; on the one hand, this significantly ex
pands the number of liquid-crystalline substances and, on the
other hand, it also allows the creation of other new types of
macromolecular compounds. Polymers of this type are now be
ing synthesized and widely studied in polymer laboratories
in the FRG, USA, USSR, UK, Japan, France, and other countries
and, together with other liquid-crystalline polymers with a
linear structure, are the subject of discussion at interna
tional conferences and symposia. Within the International
Union of Pure and Applied Chemistry (IUPAC), the European
Physical Society, and the American Chemical Society alone,
there have been more than 20 international meetings of scien
tists concerned with questions relating to the examination of
problems of liquid-crystalline ordering in polymers and their
synthesis during 1982-1985, not to mention the many national
symposia and conferences.
Many reviews and collections published in the FRG, USA,
and USSR (see the references to the Introduction and to Chap
ter 4) have been dedicated to the chemistry and physics of
polymeric liquid crystals. In addition to other questions,
they examine the problems of the synthesis, structure, and
properties of liquid-crystalline polymers with mesogenic side
groups. Nevertheless, up to now there has not yet been any
concentrated complete analysis of the field of comb-shaped
macromolecules and the liquid-crystalline polymers based on
them; our book is the first attempt in this direction.
In comparison to the Russian edition published in 1980,
the contents of this monograph have been significantly re
vised. Basic changes were made in the chapters on the liquid
crystalline state, which have actually been rewritten in con
sideration of the important new publications which appeared
in 1980~1984, and a totally up-to-date picture of the status
of this field and the trends in its development is provided.
PREFACE vii
Chapters on the structure and molecular mobility of comb
shaped polymers in the solid phase and in solutions have been
added, although the subject matter and exposition style have
generally remained the same. At the same time, we believed
it possible to exclude two sections which are not very impor
tant for understanding the entire field as a whole: those
which deal with the structures of gels of linear block copoly
mers and problems of the radical polymerization of higher
alkyl methacry1ates. The discussion of the properties of
gels of comb-shaped macromolecules was moved to another chap
ter.
We would like to thank our colleagues of many years, Dr.
Raisu Tal'roze, Dr. Yakov Freidzon, and Dr. Sergei Kostromin,
for their useful discussions on liquid crystals reported in
this monograph, and A1eksei Plate for his assistance in pre
paring the graphs and illustrations.
N. A. Plate and V. P. Shibaev
Moscow
June, 1985
Contents
Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Chapter 1
Structure of Comb-Shaped Polymers
1.1. Early Studies ................................. . 9
1.2. The Amorphous State ........................... . 13
1.3. The Crystalline State of Isotactic Po1y(1-a1ky1
ethy1ene)s, Po1y(1-a1ky1 ethylene oxide)s, and
Po1y(a1ky1 a1dehyde)s .......................... . 21
1.4. The Rotational-Crystalline State .............. . 39
1.4.1. Hexagonal Packing ..................... . 39
1.4.2. d Spacings. Sing1e- and Two-Layer Pack-
ing of the Side Chains ................ . 52
1.4.3. Heats of Fusion, Length of Crystalliz
able Sequences of Units, and Conver-
gence Temperature ..................... . 75
1.5. Crystallization of Comb-Shaped Copolymers ..... . 85
1.6. Supermolecular Structure ...................... . 93
References 96
Chapter 2
Molecular Mobility in Comb-Shaped Polymers
2.1. Effect of the Phase State on the Relaxation
Properties ..................................... 105
2.1.1. Polyethylene and Isotactic Po1y(1-a1ky1
ethy1ene)s ............................. 106
2.1. 2. Amorphous Comb-Shaped Polymers ......... 112
2.1.3. Crystalline Comb-Shaped Polymers ....... 121
2.1.4. Concluding Comments .................... 128
ix
x CONTENTS
2.2. Rheological Properties of Comb-Shaped Poly(alkyl
acrylate)s and Poly(l-alkyl ethylene)s .....•.. 131
References .....•....•................•.•....•....•.. 139
Chapter 3
Comb-Shaped Macromolecules in Solutions
and Intramolecular Interactions
3.1. Optical Anisotropy ............•.•.••••.•.•..•. 146
3.2. Conformational State and Intramolecular Mobil-
i ty .•••.•.•........•.•..•••.•....•.........••. 157
3.3. Unperturbed Dimensions of the Macromolecules .. 169
3.4. Gel Formation in Solutions of Comb-Shaped Poly-
mers 173
References ......•..•.••.•••..•....•.••••....•.•.•.•. 191
Chapter 4
Thermotropic Liquid-Crystalline Polymers
4.1. General Information on the Formation and Struc-
ture of Low-Molecular-Weight Liquid Crystals •. 199
4.2. The Liquid-Crystalline State in Linear Poly-
mers •.......•......••.......•.•..•.......•...• 205
4.3. Synthesis of Liquid-Crystalline Polymers with
Mesogenic Side Groups and Some Features of the
Formation of Mesophases •...•...•........•.•... 217
4.4. Comb-Shaped Liquid-Crystalline Polymers .•••... 244
4.5. Features of the Properties of Thermotropic
Liquid-Crystalline Polymers Correlated with
Their Macromolecular Nature .•.•..•.•.•.••.•... 247
4.6. Theory of the Liquid-Crystalline Ordering of
Melts of Linear and Branched Macromolecules
with Mesogenic Groups in the Main and Side
Chains ...•.•••.•.•............•..•.•....•...•. 258
4.7. Mechanisms of the Formation and Properties of
the Smectic, Nematic, and Cholesteric Meso-
phases of Liquid-Crystalline Polymers with
Mesogenic Side Groups .•.....•.•.•••..••.•••... 267
4.7.1. Smectic Mesophases •..........•..•••.•. 268
4.7.1.1. Chemical Structure and Thermal
Properties ..........•.•..........• 268
4.7.1.2. Structure of Smectic Mesophases ... 271
4.7.1.2.a. SA Mesophases.................. 278
CONTENTS xi
4 . 7 . 1. 2 . b. SB. SE' and SF Mesophases
and Other Types of Structures
with Translationally Ordered
Groups in Layers ..........•.. 281
4.7.1.2.c. Sc Mesophases................. 290
4.7.1.3. Some General Comments on the
Structure of Smectic Polymers .... 295
4.7.2. Nematic Mesophase ........•..........• 309
4.7.3. Comparison of Some Properties of Smectic
and Nematic Liquid -Crystalline Polymers. 317
4.7.3.1. Homopolymers..................... 317
4.7.3.l.a. The Order Parameter .......... 318
4.7.3.l.b. Rheological Properties .... ... 323
4.7.3.l.c. Molecular Mobility in the
Solid State .................. 326
4.7.3.2. Copolymers ....................... 331
4.7.3.2.a. Copolymers of Mesogenic and
Nonmesogenic Monomers ........ 331
4.7.3.2.b. Copolymers of Two Mesogenic
Monomers ..................... 333
4.7.4. The Cholesteric Mesophase ............ 337
4.7.4.1. Optical Properties ...••....•..... 347
4.7.4.2. The Structure of Cholesteric Poly-
mers ............................. 356
4.8. Behavior of Liquid-Crystalline Polymers in
Electrical and Magnetic Fields ............... 359
4.8.1. Orientational Effects ...... ..... ..... 361
4.8.1.1. The Concept of Electro- and
Magnetooptical Effects in Low-
Molecular-Weight Liquid Crystals .. 361
4.8.1.2. Comb-Shaped Liquid-Crystalline
Polymers .................••...... 363
4.8.l.2.a. The Fredericks Transition (S
Effect) ...................... 363
4.8.l.2.b. Orientation in a Magnetic
Field ........................ 373
4.8.1.2.c. The "Guest-Host" Effect...... 375
4.8.l.2.d. Optical Recording of Informa-
tion (Thermal Addressing) .... 376
4.8.l.2.e. The Structural Transition In-
duced by an Electric Field ... 378
4.8.2. Electrohydrodynamic Effects .......... 380
4.9. Behavior of Liquid-Crystalline Polymers with
Mesogenic Side Groups in Dilute Solutions .... 385
References ..........•................•............. 397