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  • POLYMER-DISPERSED AND POLYMER-STABILIZED LIQUID CRYSTALS

    A dissertation submitted to Kent State University in partial

    fulfillment of the requirements for the degree of Doctor of Philosophy

    by

    Sarah Elizabeth Hicks

    May 2012

  • All rights reserved

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    ProQuest LLC.789 East Eisenhower Parkway

    P.O. Box 1346Ann Arbor, MI 48106 - 1346

    UMI 3510749

    Copyright 2012 by ProQuest LLC.

    UMI Number: 3510749

  • ii

    Dissertation written by Sarah Elizabeth Hicks

    B.M.E., Florida State University, 2000 M.S., University of Southern Mississippi, 2006

    Ph.D., Kent State University, 2012

    Approved by ____________________________________, Chair, Doctoral Dissertation Deng-ke Yang ____________________________________, Members, Doctoral Dissertation Qi-huo Wei _____________________________________, Liang-Chy Chien _____________________________________, Eugene Gartland _____________________________________, Alexander Seed

    Accepted by

    _____________________________________, Chair, Department of Chemical Physics Hiroshi Yokoyama _____________________________________, Dean, College of Arts and Sciences John R.D. Stalvey

  • iii

    TABLE OF CONTENTS

    TABLE OF CONTENTS....iii

    LIST OF FIGURES.........vi

    LIST OF TABLES....x

    ACKNOWLEDGEMENTS.....xi

    REFERENCES.138

    Chapter Page

    1. Introduction.......1

    1.1 Liquid Crystal Polymer Composites....1

    1.2 Dissertation Overview......2

    2. Liquid Crystals and Polymer Dispersed Liquid Crystals..........................................................4

    2.1 Discovery of Liquid Crystals: The Intermediate Phase....................................................4

    2.2 The Order of Liquid Crystals...........................................................................................8

    2.3 Deformations of Liquid Crystals......................................................................................9

    2.4 Optics of Liquid Crystals...............................................................................................11

    2.5 Electrical Properties of Liquid Crystals.........................................................................13

    2.6 Applications of Liquid Crystals.....................................................................................15

    2.7 Liquid Crystal Polymer Dispersions..............................................................................21

    2.8 Phase Separation in LCPDs............................................................................................24

    3. Defect Studies and Shape Changes of Liquid Crystal Polymer Droplets Under Applied

    Fields.......................................................................................................................................29

  • iv

    3.1 Introduction....................................................................................................................29

    3.2 Experiment.....................................................................................................................35

    3.3 Results............................................................................................................................35

    3.4 Conclusion......................................................................................................................44

    4. Molecular Freezing by Polymer Network in Nematic Liquid Crystals.46

    4.1 Introduction....................................................................................................................46

    4.2 Experiment.....................................................................................................................48

    4.3 Results........................................................................................................................... 51

    4.4 Conclusion......................................................................................................................66

    5. Electro-Optic Studies of Vertical Alignment Mode Liquid Crystal Displays through

    Polymer Stabilization............................................................................................................68

    5.1 Introduction....................................................................................................................68

    5.2 Experiment.....................................................................................................................72

    5.3 Results............................................................................................................................74

    5.4 Conclusion..................................................................................................................... 90

    6. Tuning of Reflective Cholesteric Liquid Crystal Displays by Polymer Stabilization....... ..91

    6.1 Introduction................................................................................................................... 91

    6.2 Experiment.....................................................................................................................94

    6.3 Results............................................................................................................................97

    6.4 Conclusion....................................................................................................................110

    7. Microstructures on Liquid Crystal Elastomer Materials....................................................112

    7.1 Introduction..................................................................................................................112

    7.2 Experiment...................................................................................................................115

    7.3 Results..........................................................................................................................119

  • v

    7.3.1 Soft Lithography...................................................................................................119

    7.3.2 Hard Lithography.................................................................................................126

    7.4 Conclusions.................................................................................................................131

    8. Conclusion...........................................................................................................................134

    8.1 Dissertation Summary..................................................................................................134

    8.2 Future of Liquid Crystal Polymer Composites.............................................................136

  • vi

    LIST OF FIGURES

    Figure 1 Nematic phase of a liquid crystal....................................................................................6 Figure 2 Smectic phase of a liquid crystal.....................................................................................7 Figure 3 Cholesteric phase of a liquid crystal...............................................................................8 Figure 4 Plot of order parameter as a function of temperature for a liquid crystal.......................9 Figure 5 Three types of liquid crystal deformations....................................................................10 Figure 6 Refractive indices of a liquid crystal molecule.............................................................12 Figure 7 Graph of refractive index over temperature for a nematic liquid crystal......................12 Figure 8 Representation of liquid crystals in response to electric fields.....................................14 Figure 9 Freedericksz transition in a liquid crystal......................................................................15 Figure 10 Dynamic mode liquid crystal display..........................................................................17 Figure 11 Twisted nematic liquid crystal display........................................................................17 Figure 12 Vertical alignment mode liquid crystal display...........................................................19 Figure 13 In-plane switching mode liquid crystal display...........................................................19 Figure 14 Liquid crystal based biosensor....................................................................................20 Figure 15 Polymer dispersed liquid crystal.................................................................................22 Figure 1

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