Surfaces and Interfaces of Liquid Crystals

✍ Scribed by Theo Rasing, Igor Musevic

• Year: 2004
• Tongue: English
• Leaves: 312
• Edition: 1
• Category: Library

✦ Synopsis

This book describes the state of the art of our understanding of liquid-crystal interfaces on a molecular level. The interactions of liquid crystal molecules with a surface play an essential role in the operation of liquid crystal displays (LCD's) and other LC devices that are based on the controllable anchoring of LC molecules on polymer coated surfaces. This book addresses the microscopic interaction between a macromolecule (liquid crystal, polymer) and a wall, using state of the art surface and interface-sensitive experimental techniques, such as Atomic Force Microscopy (AFM), Scanning Tunneling Microscopy (STM), Linear and Nonlinear Optical Microscopy and (Dynamic) Light Scattering (DLS). These experimental techniques were complemented with computer simulations and supra molecular chemistry methods to develop controllable polymeric surfaces.

✦ Table of Contents

SURFACES AND INTERFACES OF LIQUID CRYSTALS......Page 1
Title Page......Page 3
Copyright Page......Page 4
Contents......Page 5
List of Contributors......Page 11
Prologue......Page 15
Igor Muševič, Cindy Nieuwkerk and Theo Rasing......Page 17
1.1 Surface Alignment, Length-scales, Symmetry and Microscopic Interactions......Page 18
Rubbing......Page 22
Photoalignment......Page 23
Alignment by Nanostructuring Polymer Surfaces......Page 26
1.3 Overview of the Contents of the Book......Page 27
References......Page 28
2.1 Introduction......Page 31
2.2 Liquid Crystals in Cylindrical Cavities......Page 33
2.3 Order in Ultrathin Molecular Layers Detected by NMR......Page 42
2.4 Deuteron Spin Relaxation Above T NI......Page 47
2.5 Conclusions......Page 52
References......Page 53
Igor Muševič......Page 55
3.1.1 Introduction......Page 56
3.1.2 Measuring Interfacial Forces on a Molecular Scale with an Atomic Force Microscope......Page 57
3.1.3 First Adsorbed Layer of Cyanobiphenyl Molecules on Silanated Glass......Page 59
3.1.4 Pre-nematic Mean-field Surface Interaction in the Isotropic Phase......Page 62
3.1.5 Capillary Condensation of the Nematic Phase in Confinement......Page 65
3.1.6 Pre-smectic Interaction......Page 68
3.1.7 Smectic Capillary Condensation......Page 70
3.2.1 Introduction......Page 71
3.2.2 AFM Force Spectroscopy......Page 72
3.2.3 Structural Force in Confined Smectics......Page 74
3.2.4 Smectic Period from AFM Force Spectroscopy......Page 75
3.2.5 Smectic Compressibility Modulus......Page 78
3.3 Surface Forces in Thin Layers of Liquid Crystals as Probed by Surface Force Apparatus — SFA......Page 79
3.3.1 The Surface Force Apparatus......Page 80
3.3.2 Structural Forces in the Smectic A Phase......Page 83
3.3.3 Surface Order Forces: Layering in Non-layered Materials......Page 86
3.3.4 Force and Refractive Index in Thermotropic Nematics......Page 89
References......Page 93
Igor Muševič......Page 97
4.1.1 Brewster Angle Ellipsometry of the Isotropic Nematic-glass Interface......Page 99
4.1.2 Photoelastic Modulator Based Ellipsometer......Page 102
4.1.3 Ellipsometry of the Glass-Isotropic Nematic Liquid Crystal Interface......Page 104
4.1.4 Ellipsometry of the Glass-Isotropic Smectic Liquid Crystal Interface......Page 106
4.1.5 Evaporation of 8CB on PVCN Coated Glass Substrate......Page 107
4.2.1 Thermal Fluctuations in Nematic Liquid Crystals......Page 110
4.2.2 Fluctuation Modes in Confined Liquid Crystals......Page 111
4.2.3 Dynamic Light Scattering Experiment......Page 114
4.2.4 Measuring the Anchoring Coefficients......Page 118
4.2.5 Aging of Photoaligning Layers......Page 119
4.2.6 Temperature Dependence of the Anchoring Coefficients......Page 120
References......Page 121
5.1 Introduction......Page 125
5.2 Second Harmonic Generation from Surfaces and Interfaces......Page 126
5.3 SHG Study of Surface Nematic Order Induced by Rubbed Silane Derivatives......Page 132
5.4 SHG Study of Photo-induced Changes in Poly(vinyl) Cinnamate (PVCN)......Page 133
Effect of Unpolarized UV Light......Page 134
Effect of Polarized UV Light......Page 136
Surface Order Parameter......Page 137
Over-writing of Optically Induced Alignment......Page 139
5.5 SHG Study of Liquid Crystal Alignment on PVCN......Page 140
LC Deposition on the LPP Substrates......Page 142
5.6 Structure of Multilayer 8CB Films Evaporated onto Solid Substrates......Page 143
Polarity of 8CB Multilayer......Page 146
Growth Stages of 8CB......Page 147
5.7 Conclusion......Page 148
References......Page 149
6.1 Introduction......Page 153
6.2 Principle and Properties of NEXAFS Spectroscopy......Page 154
6.3 Molecular Orientation Factors......Page 158
6.4 Experimental Setup for NEXAFS Spectroscopy......Page 160
6.5 Polarization Dependent NEXAFS Spectra of Polyimide and Polystyrene Surfaces......Page 163
Unrubbed Films......Page 164
Rubbed Films......Page 165
Orientation Factors of Rubbed Films......Page 167
Origin of the Molecular Reorientation in the Rubbing Process......Page 170
6.6 Molecular Anisotropy and Liquid Crystal Alignment on Rubbed Polymer Surfaces......Page 171
6.7 NEXAFS Study of Ion Beam Irradiated Polymer Surfaces......Page 176
6.8 Replacing the Polymer: Ion Beam Irradiated Amorphous Carbon......Page 179
Acknowledgment......Page 185
References......Page 186
7.1 STM Investigations of the Ordering of 8CB Molecules on Graphite......Page 189
7.2.1 Introduction......Page 195
7.2.2 AFM Patterning......Page 197
7.3.1 Introduction......Page 200
7.3.2 Electrostatic Force Between Surfaces in Liquids......Page 201
7.3.3 AFM Observation of Force Due to Charged Interfaces......Page 203
7.4 Electric Force Microscope Observations of Electric Surface Potentials......Page 208
7.4.1 Principle of Operation of Electric Force Microscope......Page 209
7.4.2 Inorganic Ferroelectric Films......Page 212
7.4.3 Organic Ferroelectric Films......Page 215
7.4.4 A Simple Model of Electric Force Microscopy......Page 217
7.4.5 EFM Measurements on Rubbed Substrates for Liquid Crystal Alignment......Page 218
7.4.6 Conclusions......Page 221
References......Page 222
8.1 Introduction......Page 225
8.2 Microscopic versus Macroscopic Theoretical Aspects......Page 226
8.2.1 Microscopic Models......Page 229
8.2.2 Macroscopic Models: Phenomenological Landau—de Gennes Theory......Page 231
8.2.3 Fluctuations of the Order Parameter......Page 234
Correlation Lengths of the Nematic Order Parameter......Page 235
8.3 Confined Nematogenic Systems......Page 237
8.3.1 Heterophase Ordering: Wetting Effects......Page 238
Fluctuations of the Degree of Order......Page 240
Biaxial Fluctuations......Page 241
Director Fluctuations......Page 242
8.3.3 Ordering in a Frustrated Nematic: Hybrid Nematic Cell......Page 243
Bent-director Structure......Page 244
Biaxial Configuration......Page 245
8.3.4 Monte Carlo Simulations of a Hybrid Cell......Page 246
8.3.5 Pretransitional Dynamics in a Hybrid Nematic Cell......Page 248
Director and Biaxial Fluctuations......Page 249
8.4 Forces Acting on a Thin Liquid-crystalline Film......Page 250
Heterophase Systems: Nematic Order Variation......Page 251
Frustrated Systems: General Deformation of Order......Page 252
8.4.2 Pseudo-Casimir Force......Page 253
Heterophase Systems: Order Parameter Variation......Page 254
Frustrated System: Hybrid Nematic Cell......Page 255
8.5 Experimental Evidence of Structural and Pseudo-Casimir Forces in Liquid Crystals......Page 256
References......Page 259
9.1 Introduction......Page 263
9.2 Current market situation......Page 266
9.3 Large Size LCD — Attempts Towards Wide Viewing Angle LCDs......Page 268
9.3.1 New LCD Configuration for a Wide Viewing Angle LCD......Page 274
9.3.2 Demonstration of Dual Domain LCD......Page 276
9.4 Performance Boost in Small Portable Displays Enabled by Director Control of LC Networks in Retardation Foils......Page 279
9.4.1 The Reactive Mesogen Technology Applied for Uniaxial and Biaxial Optical Fetarders......Page 280
9.4.2 Application in a Transflective LCD......Page 283
9.4.3 Ultimate LCD Performance by Local Director Variations in Both LC Layer and Retardation Foils......Page 287
9.5 Ion Beam Treated Amorphous Carbon Films for LCD Applications......Page 288
References......Page 291
Epilogue......Page 295
Acknowledgements......Page 297
Index......Page 299
Back Cover......Page 312