Liquid Crystals: Viscous and Elastic Properties

Liquid Crystals: Viscous and Elastic Properties......Page 5
Contents......Page 7
Preface......Page 13
1 Introduction......Page 15
References......Page 18
2.1.1 Liquid Crystal Molecules and Phases......Page 21
2.1.2 Nonliquid Crystal Compounds......Page 26
2.1.3 Typical Methods of Liquid Crystal Material Preparation for Various Applications......Page 28
2.1.4 Basic Physical Properties......Page 30
2.1.4.1 Dielectric Properties......Page 31
2.1.4.2 Optical Anisotropy......Page 35
2.1.4.4 Elasticity......Page 38
2.1.4.5 Viscosity......Page 40
2.2 Liquid Crystal Alignment on the Surface......Page 44
2.2.1.1 Electrooptical Cells......Page 45
2.2.1.2 Planar (Homogeneous) Orientation......Page 46
2.2.1.3 Homeotropic Orientation......Page 48
2.2.1.4 Tilted Orientation......Page 50
2.2.1.5 Other Types of Liquid Crystal Alignment......Page 51
2.2.2 Surface Energy......Page 53
2.3 Liquid Crystals Under Magnetic and Electric Fields......Page 55
References......Page 56
3.1 Couette and Poiseuille Flows in Isotropic Liquids and Liquid Crystals......Page 59
3.2 Hydrodynamic Instabilities in Couette and Poiseuille Steady Shear Flows......Page 62
3.3.1 Homogeneous Instability at Initial Planar Orientation Normal to the Flow Plane......Page 63
3.3.3 Instability at Initial Planar Orientation in the Flow Plane......Page 68
3.3.4 Hydrodynamic Instabilities at Initial Homeotropic Orientation......Page 69
3.3.5 Orientational Instability in a Nematic Liquid Crystal in a Decaying Poiseuille Flow......Page 72
3.3.6 Influence of a Decay Flow on Electrohydrodynamic Instability in Liquid Crystals......Page 78
3.4.1 Oscillating Coutte Flow......Page 80
3.4.2 Oscillating Poiseuille Flow: Planar Orientation......Page 82
3.4.3 Oscillating Poiseuille Flow: Homeotropic Orientation......Page 84
3.4.3.1 Experimental Setup for Low-Frequency Poiseuille Flow......Page 85
3.4.3.2 Linear In-Plane Motion of a Director Under Oscillating Poiseuille Flow......Page 88
3.4.3.3 Hydrodynamic Instabilities Under Oscillating Poiseuille Flows......Page 95
3.5.2 Secondary Roll Instability in Oscillating Flow......Page 104
3.5.3 Long-Living Domains Produced by Flows......Page 107
3.6.1 Linear Oscillating Flows at Weak Anchoring......Page 109
3.6.1.1 General Equations......Page 110
3.6.1.2 Linear Oscillating Flow at Symmetrical Boundary Conditions......Page 112
3.6.1.3 Linear Oscillating Flow at Hybrid Boundary Conditions......Page 114
3.6.1.4 Experimental Technique and Results......Page 115
3.6.2 Hydrodynamic Instabilities at Weak Anchoring......Page 117
References......Page 120
4.1 Methods and Technique of Ultrasonic Investigations of Liquids and Liquid Crystals: Longitudinal Waves......Page 125
4.1.1 Impulse Method......Page 128
4.1.2 Resonator Method......Page 131
4.1.3.1 Peculiarities of Ultrasonic Investigations of Liquid Crystals......Page 132
4.1.3.2 Ultrasonic Chambers for the Study of Liquid Crystals......Page 133
4.2.1 Theoretical Background......Page 135
4.2.2.1 Static Regime......Page 140
4.2.2.2 Dynamic Regime......Page 144
4.3.1 Shear Waves in Isotropic Liquids......Page 148
4.3.2 Peculiarities of Shear Waves in Liquid Crystals......Page 150
4.3.3 Experimental Methods for Shear Wave Studies......Page 151
4.4.1 Phase Transitions and Critical Phenomena in Liquid Crystals: General Aspects and Peculiarities of Ultrasonic Studies......Page 156
4.4.2 Nematic–Isotropic Transition......Page 158
4.4.3 Nematic–Smectic A Transition......Page 162
4.4.4 Critical Dynamics and Viscoelastic Properties at Smectic A–Smectic C Phase Transition......Page 169
4.4.5 Ultrasonic Studies of Phase Transitions in Confined Liquid Crystal Systems......Page 181
References......Page 187
5.1 Methods for Measurements of Frank.s Elastic Constants of Liquid Crystals......Page 193
5.1.1 Optical Methods Based on Fr eedericksz Transition......Page 194
5.1.2 Light Scattering Method......Page 200
5.2.1 Measurements in Bulk Samples of Nematic Liquid Crystals......Page 209
5.2.1.1.1 Permanent Rotation of Magnetic Field......Page 210
5.2.1.1.2 Step-Like Rotation of Magnetic Field......Page 213
5.2.2 Measurements in Thin Layers of Nematics......Page 214
5.2.3 Rotational Viscosity of Smectic C Phase......Page 220
5.3 Viscosimetry of Liquid Crystals in Shear Flows......Page 234
5.3.1 Measurements of Anisotropic Shear Viscosities in Flows of Liquid Crystals Stabilized by Fields......Page 236
5.3.1.1 Poiseuille Flow in Flat Capillary......Page 237
5.3.1.2.1 Viscosity Measurements at a Steady Simple Shear Flow......Page 243
5.3.1.2.2 Measurements in Low-Frequency Oscillating Flows......Page 244
5.3.2 Measurements of Anisotropic Shear Viscosities in Flows of Liquid Crystals Stabilized by Surfaces......Page 246
5.4 Optical Methods for the Measurement of Leslie Coefficients......Page 254
5.4.1.1 Measurement in a Steady Simple Shear Flow......Page 255
5.4.1.2 Measurement in Oscillating Simple Shear Flows......Page 257
5.4.2 Measurements by Using Quasielastic Light Scattering......Page 258
5.4.3 Determination of Leslie Coefficients from the Dynamics of Fr eedericksz Transitions......Page 263
5.5.1 Surface Anchoring Parameters......Page 266
5.5.2.1 Field-Off Techniques......Page 268
5.5.2.1.1 Light Scattering Methods......Page 269
5.5.2.1.2 Torque Balance Method......Page 271
5.5.2.2 Field-On Techniques......Page 272
5.5.3 Surface Dynamics of Liquid Crystals......Page 278
References......Page 287
6.1.1.1 Static Director Distribution......Page 297
6.1.1.2 Effect of a Weak Anchoring at the Boundaries......Page 299
6.1.1.3 Dynamics of the Director Motion: Backflow Effect......Page 301
6.1.1.4 Optical Response......Page 303
6.1.2 Twist Effect......Page 310
6.1.2.1.1 Twist-Cell Geometry for Zero Voltage: Mauguin Conditions......Page 312
6.1.2.1.2 Transmission–Voltage Curve for Normal Light Incidence......Page 314
6.1.2.1.3 Viewing Angle Dependences of Twist LCDs......Page 317
6.1.2.1.4 Principles of Passive Matrix Addressing of Twist LCDs......Page 319
6.1.2.1.5 Dynamics of the Twist Effect......Page 321
6.1.2.1.6 New Developments......Page 322
6.1.3.1 Discovery of Supertwist Effect for LCDs: SBE Mode......Page 324
6.1.3.2 Various Supertwist Modes......Page 327
6.1.3.3 Dependence of TVC Steepness on the Material and Construction Parameters......Page 328
6.1.3.4 Supertwisted LCDs with Improved Characteristics: STN-LCDs with Phase Retardation Plates......Page 329
6.1.3.5 Double-STN-Cell (DSTN) Configuration: Triple STN Subtractive Color System......Page 330
6.1.3.6 Multiline Addressing: Shadowing......Page 331
6.1.4.1 Selective Reflection Band......Page 332
6.1.4.3 Linear Flexoelectric Effect......Page 333
6.1.4.4 Reflective Cholesteric Structures......Page 334
6.1.5.1.1 Structure and Symmetry......Page 337
6.1.5.1.5 Rotational Viscosities......Page 338
6.1.5.1.7 Dielectric and Optical Properties......Page 340
6.1.5.1.8 Elastic Properties and Anchoring Energy......Page 342
6.1.5.1.9 Aligning and Textures......Page 344
6.1.5.1.10 Electrooptic Effects in FLC Cells......Page 347
6.1.5.1.11 Addressing Principles of Passive Ferroelectric LCDs......Page 356
6.2.1 Various LCD Addressing Schemes......Page 360
6.2.2 Passive Matrix Displays......Page 362
6.2.3 Active Matrix Displays......Page 365
6.2.4.1.1 BTN with 0 <=> π Twist Angle Switching......Page 370
6.2.4.1.3 Optically Rewritable LCDs......Page 372
6.3 LC Applications in Photonics: Passive Optical Elements for Fiber Optical Communication Systems......Page 374
6.3.1 LC Switches......Page 375
6.3.2 Other LC Passive Elements for Photonics Applications......Page 378
6.3.3 Photonic Crystal/Liquid Crystal Structures......Page 381
6.3.4 Photoalignment Technology for LC Photonics Devices......Page 382
References......Page 386
7.1 Liquid Crystals as Sensors of Mechanical Perturbations: Physical Background and Main Characteristics......Page 393
7.2.1 Decreasing Threshold Pressure Gradient via Choice of Optimal Geometry......Page 398
7.2.2 Use of Electric Fields......Page 401
7.3.1 Liquid Crystal Sensors of Differential Pressure......Page 408
7.3.2 Liquid Crystal Sensors of Acceleration, Vibrations, and Inclination......Page 412
7.4 Liquid Crystals for the Control of Liquid and Gas Flows......Page 416
7.5 Application of Liquid Crystals for Detecting and Visualizing Acoustic Fields......Page 419
7.5.1 Acoustic Flows in Liquid Crystals......Page 420
7.5.2 Acoustooptical Effects on Liquid Crystals in the Presence of Electric and Magnetic Fields......Page 422
References......Page 427
Index......Page 431