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OCR for page R1
Liquicl Crystalline Polymers
Report of the
Committee on Liquid Crystalline Polymers
NATIONAL MATERIALS ADVISORY BOARD
Commission on Engineering and Technical Systems
National Research Council
NMAB-453
National Academy Press
1990
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NOTICE: The project that is the subject of this report was approved by the Governing Board of the
National Research Council, whose members are drawn from the councils of the National Academy
of Sciences, the National Academy of Engineering, and the Institute of Medicine. The members of
the committee responsible for the report were chosen for their special competences and with regard
for appropriate balance.
This report has been reviewed by a group other than the authors according to procedures
approved by a Report Review Committee consisting of members of the National Academy of
Sciences, the National Academy of Engineering, and the Institute of Medicine.
The National Academy of Sciences is a private, nonprofit, self-perpetuating society of
distinguished scholars engaged in scientific and engineering research, dedicated to the furtherance
of science and technology and to their use for the general welfare. Upon the authority of the charter
granted to it by the Congress in 1863, the Academy has a mandate that requires it to advise the
federal government on scientific and technical matters. Dr. Frank Press is president of the National
Academy of Sciences.
The National Academy of Engineering was established in 1964, under the charter of the
National Academy of Sciences, as a parallel organization of outstanding engineers. It is autonomous
in its administration and in the selection of its members, sharing with the National Academy of
Sciences the responsiblity for advising the federal government. The National Academy of
Engineering also sponsors engineering programs aimed at meeting national needs, encourages
education and research, and recognizes the superior achievements of engineers. Dr. Robert M. White
is president of the National Academy of Engineering.
The Institute of Medicine was established in 1970 by the National Academy of Sciences to
secure the services of eminent members of appropriate professions in the examination of policy
matters pertaining to the health of the public. The Institute acts under the responsibility given to
the National Academy of Sciences by its congressional charter to be an adviser to the federal
government and, upon its own initiative, to identify issues of medical care, research, and education.
Dr. Samuel O. Thier is president of the Institute of Medicine.
The National Research Council was organized by the National Academy of Sciences in 1916
to associate the broad community of science and technology with the Academy's purposes of
furthering knowledge and advising the federal government. Functioning in accordance with general
policies determined by the Academy, the Council has become the principal operating agency of both
the National Academy of Sciences and the National Academy of Engineering in providing services
to the government, the public, and the scientific and engineering communities. The Council is
administered jointly by both Academies and the Institute of Medicine. Dr. Frank Press and Dr.
Robert M. White are chairman and vice chairman, respectively, of the National Research Council.
* ** * * * * ** ** * * * *** ***
This study by the National Materials Advisory Board was conducted under Contract No.
MDA903-89-K-0078 with the Department of Defense and the National Aeronautics and Space
Administration.
Library of Congress Catalog Card Number 90-60385.
International Standard Book Number 0-309-04231-3.
This report is available from the Defense Technical Information Center, Cameron Station,
Alexandria, VA 22304-6145.
S1 10
Cover: Schematic arrangement of molecules in the smectic phase (top left} and the nematic phase
(bottom right) of a liquid crystalline material.
Printed in the United States of America.
F~stPrinung, J~mel990
Second Printing, S~p~mberl991
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ABSTRACT
The remarkable mechanical properties and thermal stability of fibers fabricated from liquid
crystalline polymers (LCPs) have led to the use of these materials in structural applications where
weight savings are critical. Advances in processing of LCPs could permit the incorporation of
these polymers into other than uniaxial designs and extend their utility into new areas such as
nonlinear optical devices. However, the unique feature of LCPs intrinsic orientational
order is itself problematic, and current understanding of processing with control of orientation
falls short of allowing manipulation of macroscopic orientation (except for the case of uniaxial
fibers). This report reviews the current and desirable characteristics of LCPs and identifies
specific problems and issues that must be addressed so that advances in the use of these unique
polymers can be expedited.
. · .
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PREFACE
The subject of liquid crystalline polymers (LCPs) transcends classical polymer chemistry
and physics, and it extends the conventional boundaries of rheology and processing. Properties of
these new materials are, on the one hand, reminiscent of amorphous metals, while simultaneously
exhibiting attributes of organic single crystals. In this report we attempt to evaluate the potential
of LCPs in selected areas, pointing out obstacles to further progress and suggesting where efforts
in research and development might expedite LCP utilization in current and new technologies.
Because the subject touches on a wide range of topics, we have attempted to make this
report accessible by adhering to a parallel presentation scheme. Thus, insofar as possible, the key
chapters of the report are divided into the following headings:
Macromolecular Design and Synthesis
Understanding and Theory
Processing
Mechanical Properties
Blends and Composites
Nonlinear Optical Properties
When useful, the headings are subdivided further into sections on lyotropic (solution processed)
and thermotropic (melt processed) LCPs. Occasionally, one of these sections may be partitioned
into separate subsections, e.g., mainchain and sidechain LCPs. We have also tabulated a glossary
of abbreviations and acronyms (Appendix B).
The report is intended to enable persons unfamiliar with the field to obtain a general
appreciation of LCPs in the context of conventional polymers (see Chapter 2, Background) and to
proceed to contemporary issues associated with specific topics (e.g., nonlinear optical
characteristics of LCPs). We include an appendix indicating approximate current federal funding
levels for research on these new classes of polymers (Appendix A).
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ACKNOWLEDGMENTS
The committee is indebted to the liaison representatives for keeping the discussion of LCPs
focused; special thanks also go to Stanley Wentworth for contributing the section in Chapter 3 on
environmental stability. In addition, we are very appreciative of the following individuals who
brought detailed technical material to committee meetings:
Mohamed Zaidi, Alcoa; Harvey Ledbetter, Dow Chemical Company; John Blackwell, Case
Western Reserve University; James Stamatoff, Celanese Corporation; Ian Ward, University
of Leeds; Edwin Thomas, University of Massachusetts; Brian Kushner, BDM Corporation
Paras Prasad, State University of New York at Buffalo; Richard Lytel, Lockheed
Corporation, Palo Alto; Larry Dalton, University of Southern California; Judy Chen,
Boeing Company, Seattle; Roger Morgan, MMI; James Wolf, Boeing; James Economy,
University of Illinois; lames LyerIa, Andreas Muehlebach, and Do Yoon, IBM Corporation,
San Jose; and Richard Lusignea and Adi Guitar, Foster-Miller, Inc.
Finally, the chairman expresses earnest thanks to the committee members for their
constructive contributions and enthusiastic participation in the writing of this report, and to
Marlene Crowell, who provided secretarial support to the committee throughout the course of its
deliberations.
Edward T. Samulski
Chairman
· -
V11
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COMMITTEE ON LIQUID CRYSTALLINE POLYMERS
CHAIRMAN
EDWARD T. SAMULSKI, Department of Chemistry, University of North Carolina at Chapel Hill
MEMBERS
MORTON M. DENN, Department of Chemical Engineering, University of California at Berkeley
DONALD B. DuPRE, Department of Chemistry, University of Louisville, Louisville, Kentucky
NATHAN D. FIELD, Consultant, Elkins Park, Pennsylvania (formerly, Vice-President, R&D,
Dartco Manufacturing, Inc.)
ANSELM C. GRIFFIN III, Department of Chemistry and Polymer Science, University of
Southern Mississippi, Hattiesburg
MICHAEL JAFFE, Hoechst-Celanese Research Division, Summit, New Jersey
STEPHANIE L. KWOLEK, Consultant, Wilmington, Delaware (formerly with the Du Pont
Company, Fibers Department, Pioneering Research Laboratory)
MALCOLM B. POLK, School of Textile Engineering, Georgia Institute of Technology, Atlanta
DUSAN C. PREVORSEK, Polymer Laboratory, Allied-Signal Corporation, Morristown,
New Jersey
MONTGOMERY T. SHAW, Institute of Materials Science, University of Connecticut, Storrs
UERICH SUTER, Institute for Polymers, Eidgenossische Technische Hochschule, Zurich,
Switzerland
DAVID J. WILLIAMS, Corporate Research Laboratories, Eastman Kodak Co., Rochester,
New York
LIAISON REPRESEN7~AT~ES
NORBERT BIKALES, Polymers Program, National Science Foundation, Washington, D.C.
TED HELMINIAK, Wright-Patterson Air Force Base, Ohio
TERRY ST. CLAIR, Polymer Materials Branch, National Aeronautics and Space Administration,
Langley Research Center, Hampton, Virginia
1X
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DONALD UERICH, Air Force Office of Scientific Research, Bolling Air Force Base,
Washington, D.C.
STANLEY E. WENTWORTH, U. S. Army Materials Technology Laboratory, Watertown,
Massachusetts
KENNETH WYNNE, Division of Materials Research, National Science Foundation,
Washington, D.C.
NMAB STAFF
STANLEY M. BARKIN, Associate Director and Program Officer
MARLENE R. CROWELL, Project Assistant
x
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CONTENTS
EXECUTIVE SUMMARY
Page
1. CONCLUSIONS AND RECOMMENDATIONS 5
Macromolecular Design and Synthesis 5
Theoretical Understanding 7
Processing 8
Mechanical Properties 9
Blends ant! Composites 10
Nonlinear Optical Properties 10
2. BACKGROUND 13
Macromolecular Design and Synthesis
Understanding and Theory
Processing
Mechanical Properties
Blends and Composites
Electro-Optical Properties
3.
4.
PROPERTIES OF LIQUID CRYSTALLINE POLYMERS: CURRENT
AND DESIRABLE CHARACTERISTICS
Structural Properties
Functional Properties
Environmental Stability
PROBLEMS AND ISSUES: RECOMMENDATIONS FOR
FURTHER WORK
Macromolecular Design and Synthesis
Understanding and Theory
Processing
Mechanical Properties
Blends and Composites
Nonlinear Optical Properties
X1
18
25
27
30
36
38
49
49
63
68
71
71
74
~8
81
85
92
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Page
APPENDIXES
A.
A. Current Funding Levels/Sources for LCP Research 101
B. Glossary of Abbreviations 103
C. Biographical Sketches of Committee Members 105
X11
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FIGURES AND TABLES
Figures
2.1 Schematic indication of the differences between an isotropic and a liquid
crystalline polymer fluid
2.2 An absence of translational order in the idealized nematic
2.3 Smectic stratification (lateral registration) in a polymer mesophase
2.4 Helicoidal cholesteric structure in a mainchain LCP
2.5 Condensation polymerization involving acidolysis
2.6 Representative potential thermotropic copolyesters
Page
14
16
16
17
18
19
2.7 Synthesis of polyarylamides 20
2.8 Lyotropic polyamide unit structures 21
2.9 Synthesis of PBX polymers 22
2.11
2.12
4.1
4.2
Preparation of sidechain LCPs by free radical polymerization
Preparation of sidechain LCPs by polyesterification
Examples of preparation of sicIechain LCPs by derivitization of preformed
polymers
An illustration of the hierarchical morphology in fibers
A plot of specific tensile strength vs. specific tensile modulus
showing LCPs in context with other materials
23
23
24
34
56
Compressive strength vs. torsion modulus for some rigid rod polymers 82
Temperature dependence of dynamic mechanical tensile data (10 Hz) for
HBA-HNA copolymers
· · .
x~
84
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Page
Tables
2.1
3.1
3.2
Cold-forming methods for polymers
Properties of Kevlar~ aramid fibers derived from lyotropic LCPs
Yarn properties of some reinforcing fibers from LCPs
3.3 Properties of injection molded LCP ASTM bars
31
51
54
58
3.4 Classification of LCPs according to thermal behavior 59
3.5
3.6
Effect of gauge on flexural strength and modulus (ASTM Test Bars) 59
Comparison of barrier properties of LCPs and other polymer film
3.7 Important requirements for NLO applications
3.8 Requirements for SHG applications
3.9 Requirements for optical serial switching devices
3.10 NLO materials properties (inorganic and organic)
4.1A Properties of unidirectional epoxy composite with 60% fiber loading,
0° direction
62
63
64
64
67
86
4.1B Properties of unidirectional epoxy composite with 60% fiber loading 87
4.2 LCP-content blending regimes
x~v
89
