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This new edition of the classic text incorporates the many advances in knowledge about liquid crystals that have taken place since its initial publication in 1974. Entirely new chapters describe the types and properties of liquid crystals in terms of both recently discovered phases and current insight into the nature of local order and isotropic-to-nematic transition. There is an extensive discussion of the symmetrical, macroscopic, dynamic, and defective properties of smectics and columnar phases, with emphasis on order-of-magnitude considerations, all illustrated with numerous descriptions of experimental arrangements. The final chapter is devoted to phase transitions in smectics, including the celebrated analogy between smectic A and superconductors. This new version's topicality and breadth of coverage will ensure that it remains an indispensable guide for researchers and graduate students in mechanics and engineering, and in chemical, solid state, and statistical physics.

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CONTENTS
1 LIQUID CRYSTALS : MAIN TYPES AND PROPERTIES = 1
  1.1 Introduction : what is a liquid crystal? = 1
  1.2 The building blocks = 3
    1.2.1 Small elongated organic molecules = 3
    1.2.2 Small discoid organic molecules = 6
    1.2.3 Long helical rods = 6
    1.2.4 Polymers = 8
    1.2.5 Associated structures = 9
    1.2.6 Summary = 10
  1.3 Nematics and cholesterics = 10
    1.3.1 Uniaxial nematics = 10
    1.3.2 Nematics of different symmetry = 12
    1.3.3 Cholesterics = 13
    1.3.4 Summary = 17
  1.4 Smectics = 18
    1.4.1 Smectics A = 19
    1.4.2 Smectics C = 20
    1.4.3 'Hexatic' smectics = 22
    1.4.4 'Crystalline' smectics = 24
    1.4.5 The D phase = 26
  1.5 Columnar phases = 26
    1.5.1 Hexagonal phases = 26
    1.5.2 Rectangular and oblique phases = 27
    1.5.3 'Antiphases' = 27
  1.6 More on long-, quasilong-, and short-range order = 28
    1.6.1 'Poor man's' elasticity of liquid crystals = 29
    1.6.2 Fluctuations = 31
    1.6.3 Long-range, quasilong-range, short-range order = 32
  1.7 Remarkable features of liquid crystals = 34
2 LONG-AND SHORT-RANGE ORDER IN NEMATICS = 41
  2.1 Definition of an order parameter = 41
    2.1.1 Microscopic approach = 41
    2.1.2 Macroscopic approach = 56
    2.1.3 Relation between microscopic and macroscopic approaches = 57
  2.2 Statistical theories of the nematic order = 59
    2.2.1 Mean-field calculations for hard rods and platelets = 59
    2.2.2 Mean-field theory with S² interaction = 66
    2.2.3 Computer calculations = 73
  2.3 Phenomenological description of the nematic-isotropic transition = 76
    2.3.1 Landau free energy above Tc = 76
    2.3.2 Static pretransitional effects = 78
    2.3.3 Biaxial phase = 82
    2.3.4 Failures of the mean-field approach = 85
  2.4 Mixtures = 91
    2.4.1 Importance of mixed systems = 91
    2.4.2 General trends = 92
3 STATIC DISTORTIONS IN A NEMATIC SINGLE CRYSTAL = 98
  3.1 Principles of the continuum theory = 98
    3.1.1 Long-range distortions = 98
    3.1.2 The distortion free energy = 100
    3.1.3 Discussion of the distortion-energy formula = 102
    3.1.4 Boundary effects = 108
    3.1.5 Nematics transmit torques = 116
  3.2 Magnetic field effects = 117
    3.2.1 Molecular diamagnetism = 117
    3.2.2 Definition of a magnetic coherence length = 120
    3.2.3 The Frederiks transition = 123
  3.3 Electric field effects in an insulation nematic = 133
    3.3.1 Dielectric anisotropy = 133
    3.3.2 Polarization induced by distortion (flexoelectric effect) = 135
  3.4 Fluctuations in the alignment = 139
    3.4.1 Light-scattering experiments = 139
    3.4.2 Orientation fluctuations and correlations in a nematic single crystal = 141
    3.4.3 Scattering of light by orientation fluctuations = 144
  3.5 Hydrostatics of nematics = 150
    3.5.1 Free energy and molecular field = 150
    3.5.2 Stresses and forces = 151
    3.5.3 The balance of torques = 155
4 DEFECTS AND TEXTURES IN NEMATICS = 163
  4.1 Observations = 163
    4.1.1 Black filaments ('structures a fils') = 163
    4.1.2 'Structures a noyaux' ('Schlieren structures') = 163
    4.1.3 Types of of defects = 166
  4.2 Disclination lines = 168
    4.2.1 Definition of the 'strength' = 168
    4.2.2 Distortion field around one line = 170
    4.2.3 The concept of line tension = 178
  4.3 Point disclinations = 180
    4.3.1 Instability theorem for lines of integral strength = 180
    4.3.2 Interpretation of the noyaux = 183
    4.3.3 Other observations on point defects = 184
  4.4 Walls under magnetic fields = 185
    4.4.1 180° walls = 187
    4.4.2 Walls associated with a Frederiks transition = 189
    4.4.3 Transformation from walls to lines ('pincement') = 190
  4.5 Umbilics = 194
  4.6 Surface disclinations = 194
5 DYNAMICAL PROPERTIES OF NEMATICS = 198
  5.1 The equations of 'nematodynamics' = 198
    5.1.1 Coupling between orientation and flow = 198
    5.1.2 Choice of dynamical variables = 199
    5.1.3 The entropy source for a flowing nematic = 200
    5.1.4 The laws of friction = 204
  5.2 Experiments measuring the Leslie coefficients = 209
    5.2.1 Laminar flow under a strong orienting field = 209
    5.2.2 Attenuation of ultrasonic shear waves = 213
    5.2.3 Laminar flow in the absence of external fields = 218
    5.2.4 Variable external fields = 220
    5.2.5 Inelastic scattering of light = 227
  5.3 Convective instabilities under electric fields = 230
    5.3.1 Basic electrical parameters = 230
    5.3.2 Experimental observations at low frequencies = 233
    5.3.3 The Helfrich interpretation = 236
    5.3.4 Extension to higher frequencies = 239
  5.4 Molecular motions = 245
    5.4.1 Dielectric relaxation = 245
    5.4.2 Nuclear spin-lattice relaxation = 246
    5.4.3 Acoustic relaxation = 248
    5.4.4 Translational motions = 250
    5.4.5 Temperature variation of the friction coefficients = 254
    5.4.6 Semi-slow motions above Tc = 255
6 CHOLESTERICS = 263
  6.1 Optical properties of an ideal helix = 263
    6.1.1 The planar texture = 263
    6.1.2 Bragg reflections = 264
    6.1.3 Transmission properties at arbitrary wavelengths (normal incidence) = 268
    6.1.4 Interpretation = 271
    6.1.5 Conclusions and generalizations = 279
  6.2 Agents influencing the pitch = 280
    6.2.1 Physicochemical factors = 281
    6.2.2 External fields = 286
  6.3 Dynamical properties = 294
    6.3.1 Studies on small motions in a planar texture = 295
    6.3.2 Macroscopic flow = 296
    6.3.3 Convective instabilities = 300
    6.3.4 Torques induced by a heat flux = 304
  6.4 Textures and defects in cholesterics = 308
    6.4.1 Textures = 308
    6.4.2 Singular lines = 313
  6.5 Blue phases = 320
    6.5.1 Experimental observations = 320
    6.5.2 Double twist theories = 323
    6.5.3 Landau theory = 329
7 MACROSCOPIC BEHAVIOUR OF SMECTICS AND COLUMNAR PHASES = 337
  7.1 Continuum description of smectics and columnar phases : statics = 337
    7.1.1 Choice of variables = 337
    7.1.2 Distortion free energy of (non-chiral) smectics = 341
    7.1.3 Distortion free energy of columnar phases = 349
    7.1.4 Boundary conditions = 353
    7.1.5 Particular geometries = 357
    7.1.6 Transitions induced by external forces : Helfrich-Hurault effect = 361
    7.1.7 Transitions induced by external forces : undulation by mechanical tension = 364
    7.1.8 Transitions induced by external forces : thermo-optic effect in smectics A = 369
    7.1.9 Fluctuations = 370
  7.2 Continuum description of chiral smectics and columnar phases = 376
    7.2.1 Chiral SA * and SC * = 376
    7.2.2 Chiral SC * ( SI * , SF * , and SK * ) = 377
    7.2.3 Electric terms = 379
    7.2.4 Unwinding of the helix by an electric field = 385
    7.2.5 Fluctuations = 389
    7.2.6 Surface anchoring = 390
    7.2.7 Particular geometries = 393
8 DYNAMICAL PROPERTIES OF SMECTICS AND COLUMNAR PHASES = 408
  8.1 Unified description = 408
    8.1.1 Preliminary remarks = 408
    8.1.2 Basic equations = 410
    8.1.3 Smectics A and columnar hexagonal phases = 415
    8.1.4 The undulation mode = 418
    8.1.5 Permeation mode = 420
    8.1.6 Acoustic waves = 421
    8.1.7 Transverse modes = 423
    8.1.8 SB hex and Sc hydrodynamics = 424
    8.1.9 Remarks on the mode structure = 429
  8.2 Flow properties = 430
    8.2.1 Typical geometries = 430
    8.2.2 Flow past obstacles = 435
    8.2.3 Flow alignment = 445
  8.3 Breakdown of elasticity = 452
    8.3.1 Poor man's derivation = 452
    8.3.2 Splay modulus = 454
    8.3.3 Macroscopic non-linear stress-strain relation = 455
    8.3.4 Renormalization group results = 455
  8.4 Breakdown of hydrodynamics = 457
    8.4.1 Poor man's derivation = 457
    8.4.2 More general results = 460
    8.4.3 Columnar phases = 461
    8.4.4 Experimental situation = 462
9 DEFECTS IN SMECTICS AND COLUMNAR PHASES = 466
  9.1 Observations = 466
    9.1.1 Large deformations in smectics = 466
    9.1.2 Large deformations in columnar phases = 473
    9.1.3 Dislocations = 476
    9.1.4 Disclinations = 478
    9.1.5 Walls = 483
  9.2 Dislocation and associated stress/strain = 487
    9.2.1 Distortions in smectics = 487
    9.2.2 Strain fields in columnar phases = 500
10 PHASE TRANSITIONS IN SMECTICS = 507
  10.1 The A ○ N transition = 507
    10.1.1 Mean-field description = 507
    10.1.2 The analogy with superconductors = 509
    10.1.3 Critical phenomena = 514
    10.1.4 Anisotropic scaling = 517
    10.1.5 Experimental situation = 518
    10.1.6 The search for an anisotropic fixed point = 521
    10.1.7 Nature of the N- SA transition = 522
    10.1.8 'Poor man's' dislocation unbinding transition = 524
    10.1.9 Twisted grain boundary phase = 525
    10.1.10 Current situation = 527
  10.2 Smectic A-smectic C transition = 527
    10.2.1 Superfluid analogy = 527
    10.2.2 Ginzburg criterion = 529
    10.2.3 Experimental findings = 532
    10.2.4 First-order SA ○ Sc = 532
    10.2.5 N-A-C point = 534
    10.2.6 The SA - Sc transition in two dimensions = 540
  10.3 Transitions involving hexatic phases = 547
    10.3.1 SA ○ SB Hex transition = 547
    10.3.2 Harmonics of hexatic ordering and scaling properties = 549
  10.4 Frustrated smectics = 551
    10.4.1 Experimental facts = 551
    10.4.2 Frustrated smectics model = 557
    10.4.3 Bilayer, partial bilayer smectics, incommensurate phases, and antiphases = 560
    10.4.4 Re-entrant behaviour = 568
    10.4.5 SA - SA isolated critical point and nematic bubble = 570
    10.4.6 Molecular aspects = 575
Author index = 587
Subject index = 595