Liquid Crystals : Fundamentals

by Singh, Shri; Dunmur, David A.

• ISBN13: 9789810242503
• ISBN10: 9810242506
• Format: Hardcover
• Copyright: 2003-01-01
• Publisher: World Scientific Pub Co Inc

Summary

Liquid crystals are partially ordered systems without a rigid, long-range structure. The study of these materials covers a wide area: chemical structure, physical properties and technical applications. Due to their dual nature -- anisotropic physical properties of solids and rheological behavior of liquids -- and easy response to externally applied electric, magnetic, optical and surface fields liquid crystals are of greatest potential for scientific and technological applications. The subject has come of age and has achieved the status of being a very exciting interdisciplinary field of scientific and industrial research.This book is an outgrowth of the enormous advances made during the last three decades in both our understanding of liquid crystals and our ability to use them in applications. It presents a systematic, self-contained and up-to-date overview of the structure and properties of liquid crystals. It will be of great value to graduates and research workers in condensed matter physics, chemical physics, biology, materials science, chemical and electrical engineering, and technology from a materials science and physics viewpoint of liquid crystals.

Table of Contents

Foreword	p. v
Preface	p. vii
Liquid Crystals: Main Types and Classification	p. 1
Introduction	p. 1
General Types of Liquid Crystals	p. 3
Classification Of Liquid Crystals: Symmetry and Structure	p. 4
Calamitic Thermotropic Liquid Crystals	p. 7
Non-chiral calamitic mesophases	p. 7
Chiral calamitic mesophases	p. 10
Cubic mesophases	p. 13
Liquid crystal polymers	p. 14
Mesophases of Disc-Like Molecules	p. 16
Lyotropic Liquid Crystals	p. 17
Mesogenic Materials	p. 17
Polymorphism in Liquid Crystals	p. 22
References	p. 23
Distribution Functions and Order Parameters	p. 28
Distribution Functions	p. 28
n-Particle Density Distribution	p. 30
Order Parameters	p. 33
Microscopic order parameters	p. 34
Macroscopic order parameters	p. 39
Relationship between microscopic and macroscopic order parameters	p. 42
Measurement of Order Parameters	p. 43
Magnetic resonance spectroscopy	p. 44
Polarised Raman scattering	p. 50
X-ray scattering	p. 52
References	p. 55
Physical Properties of Liquid Crystals	p. 57
Scalar Physical Properties	p. 58
Anisotropic Physical Properties	p. 61
Optical anisotropy: The refractive index	p. 62
Dielectric anisotropy: The dielectric permittivity	p. 67
Diamagnetic anisotropy: The magnetic susceptibility	p. 72
Transport properties	p. 73
Elastic Constants	p. 78
Measurement of elastic constants	p. 80
Effects of Chemical Structur on the Physical Properties	p. 86
References	p. 89
Nematic Liquid Crystals	p. 92
Essential Features of Uniaxial Nematics	p. 92
Nematics of Different Symmetry	p. 93
Structure - Property Correlations	p. 94
Core structures	p. 95
Linking groups	p. 101
End groups	p. 105
Lateral groups	p. 107
Statistical Theories of the Nematic Order	p. 109
Landau-de-Gennes theory of the uniaxial nematic-isotropic (NI) phase transitions	p. 111
The hard particle or onsager-type theories	p. 127
The Maier - Saupe (MS) type theories	p. 135
The van der Waals (vdW) type theories	p. 141
Application of density functional theory (DFT) to the NI phase transition	p. 154
Modified weighted-density approximation (MWDA)	p. 158
Calculations and results	p. 159
References	p. 165
Nematic Liquid Crystals: Elastostatics and Nematodynamics	p. 174
Elastostatics in Nematics	p. 174
Elastic continuum theory for nematics	p. 174
Uniaxial nematic phase	p. 175
Biaxial nematic phase	p. 177
Theories for the elasticity of uniaxial nematics	p. 179
Application of Landau-de-Gennes theory	p. 179
Theories based on Maier-Saupe (MS) or Onsager type molecular models	p. 182
The van der Waals type and similar theories	p. 184
Application of density functional theory	p. 188
Unified molecular theory for the elastic constants of ordered phases	p. 196
Application to uniaxial nematic phase	p. 199
Application to biaxial nematic phase	p. 201
Dynamical Properties of Nematics	p. 205
Fluid dynamics of nematics	p. 205
The laws of friction	p. 208
Molecular motions	p. 211
Dielectric relaxation	p. 211
Magnetic resonance and relaxation	p. 213
Acoustic relaxation	p. 214
Translational motions	p. 215
References	p. 216
Smectic Liquid Crystals	p. 221
Symmetry and Characteristics of Smectic Phases	p. 221
Smectics with liquid layers	p. 223
Smectics with bond-orientational order	p. 224
Smectics with ordered layers	p. 227
Structure-Property Relations	p. 227
Smectic A Phase	p. 232
Elasticity of smectic A phase	p. 232
The basic equations	p. 232
Transition induced by external forces: Helfrich-Hurault deformation	p. 238
Correlations in the smectic A phase	p. 240
Molecular theory for the elasticity of S[subscript A] phase	p. 242
The Nematic to Smectic A (N S[subscript A]) Transition	p. 244
Phenomenological description of the NS[subscript A] transition	p. 247
Mean-field description of the NS[subscript A] transition	p. 250
Application of density functional theory to the NS[subscript A] transition	p. 259
Polymorphism in S[subscript A] Phase	p. 264
Frustrated smectics model	p. 267
Smectic C Phase	p. 271
Elasticity of smectic C phase	p. 271
Phase transitions involving S[subscript C] phase	p. 272
Smectic A--smectic C transitions	p. 273
The nematic-smectic A-smectic C (NS[subscript A]S[subscript C]) multicritical point	p. 276
Reentrant Phase Transitions (RPT) in Liquid Crystals	p. 278
Examples of single reentrance	p. 280
Examples of multiple reentrance	p. 283
Dynamical Properties of Smectics	p. 284
Basic equations of 'smectodynamics'	p. 284
Computer Simulations of Phase Transitions in Liquid Crystals	p. 287
Lebwohl-Lasher model	p. 289
Hard-core models	p. 290
Gay-Berne model	p. 295
References	p. 299
Liquid Crystals of Disc-like Molecules	p. 312
The Discotic Nematic Phase	p. 314
The Columnar Phases	p. 314
Structure-Property Relationship	p. 316
Benzene based compounds	p. 317
Triphenylene-core based compounds	p. 317
Truxene-core based compounds	p. 318
Phase Transitions in Discotic Nematic and Columnar Phases	p. 319
Continuum Description of Columnar Phases	p. 327
Uniaxial columnar phases	p. 327
Biaxial columnar phases	p. 328
References	p. 329
Polymer Liquid Crystals	p. 332
Introduction	p. 332
Types of Liquid Crystal Polymers	p. 333
Types of Monomeric Units	p. 333
Main Chain Liquid Crystal Polymers (MCLCPs)	p. 334
Side Chain Liquid Crystal Polymers (SCLCPs)	p. 335
Phase Transitions and Phase Diagrams in LC Polymers	p. 337
Nematic order in polymer solution	p. 337
Nematic order in polymer melts	p. 345
Nematic polymers with varying degree of flexibility	p. 347
Synthetic Routes and Structure-Property Relations	p. 348
Synthetic routes	p. 348
Structure-property relations	p. 351
Elastic Constants of Polymer Liquid Crystals	p. 359
References	p. 362
Chiral Liquid Crystals	p. 370
Chiral Nematic (Cholesteric) Phase	p. 371
Optical properties	p. 372
Field--induced nematic--cholesteric phase change	p. 372
Elastic continuum theory for chiral nematics	p. 373
Factors influencing the pitch	p. 374
Distortion of structure by magnetic field	p. 375
Convective instabilities under electric field: The square-lattice distortion	p. 380
Light propagation in the chiral nematic phase	p. 384
Blue Phases	p. 388
General experimental overview	p. 389
BP I and BP II--experiment	p. 391
BP III--experiment	p. 395
Theory for the blue phases	p. 396
Application of Landau theory	p. 397
Defect theory	p. 402
The bond-orientational order and fluctuation models	p. 403
Chiral Smectic Phases	p. 404
The origin of ferroelectricity	p. 404
Structure, symmetry and ferroelectric ordering in chiral smectic C phase	p. 404
Structure-property correlations in chiral smectic phases	p. 408
Continuum description of chiral S*[subscript C] (S*[subscript I], S*[subscript F] and S*[subscript K])	p. 413
Antiferroelectric and ferrielectric chiral smectic C phases	p. 414
Chiral Discotic Phases	p. 419
Chiral Polymeric Liquid Crystals	p. 420
Theory of Ferroelectricity in Chiral Liquid Crystals	p. 420
Application of Landau theory	p. 421
Molecular statistical theory for the ferroelectric order in smectics	p. 426
Microscopic models for the ferroelectric ordering in the S*[subscript C] phase	p. 426
Free energy and ferroelectric ordering of S*[subscript C] phase	p. 430
Theory for the Antiferroelectric Subphases	p. 434
Twist Grain Boundary (TGB) Phases	p. 436
References	p. 441
Lyotropic Liquid Crystals	p. 453
Amphiphilic Mesogenic Materials	p. 453
Classification and Structure of Lyotropic Liquid Crystal Phases	p. 455
The lamellar lyotropic liquid crystal phases	p. 455
The hexagonal lyotropic liquid crystal phases	p. 456
The cubic lyotropic liquid crystal phases	p. 457
Ringing gels and sponge phases	p. 458
Occurrence of Mesophases in Amphiphile/Water Systems: Phase Diagrams	p. 458
Lyotropic Nematics	p. 460
Lyotropic Liquid Crystal Polymers	p. 462
Lyomesophases in Biological Systems	p. 462
Lyomesophases formed by lipid molecules	p. 463
Lyomesophases formed by DNA derivatives	p. 465
Phase Chirality of Micellar Lyotropics	p. 465
References	p. 467
Defects and Textures in Liquid Crystals	p. 471
Classification of Defects in Liquid Crystals	p. 472
Defect textures exhibited by liquid crystals	p. 475
Dislocations (Edge and Screw)	p. 477
Schlieren defects	p. 479
Focal-conic defects	p. 481
Zigzag defects	p. 485
Defect Textures in Uniaxial Nematic Phase	p. 486
Disclinations: planar model	p. 488
Defect Textures in Biaxial Nematic Phase	p. 495
Textures and Defects in Smectics	p. 496
The smectic A phase	p. 497
The smectic C phase	p. 500
Other smectic phases	p. 500
Textures and Defects in Chiral Liquid Crystals	p. 503
The Chiral nematic (Cholesteric) phase	p. 503
Disclinations in the chiral nematic phase	p. 505
Dislocations	p. 506
Effects of the layer structure: focal-conic domains and oily streaks	p. 508
The chiral smectic C (S*[subscript C]) phase	p. 510
The blue phases	p. 511
The twist grain boundary smectic A* phase	p. 511
Defects in the Columnar Liquid Crystals	p. 513
References	p. 514
Index	p. 519
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