viii

TABLE OF CONTENTS

CHAPTER NO. TITLE PAGE NO.

ABSTRACT iii

LIST OF TABLES xv

LIST OF FIGURES xviii

LIST OF SYMBOLS AND

ABBREVIATIONS xxix

1. INTRODUCTION 1

1.1 INTRODUCTION TO LIQUID CRYSTALS 1

1.2 HISTORY OF LIQUID CRYSTALS 2

1.3 CLASSIFICATION OF LIQUID CRYSTALS 4

1.3.1 Lyotropic Liquid Crystals 4

1.3.2 Thermotropic Liquid Crystals 5

1.4 SHAPE OF MOLECULES AND

THEIR MESOPHASES 6

1.4.1 Conventional Shaped Liquid Crystal 6

1.4.1.1 Calamitic liquid crystals 7

1.4.1.2 Discotic liquid crystals 11

1.4.2 Non-Conventional Shaped Liquid Crystals 12

1.5 (ANTI) FERROELECTRICITY AND

SWITCHING MECHANISM 15

1.6 CHIRALITY IN LIQUID CRYSTALS 18

1.7 BENT-CORE LIQUID CRYSTALS 20

1.7.1 B1 Mesophase 20

1.7.1.1 Variants of B1 mesophase 23

ix

CHAPTER NO. TITLE PAGE NO.

1.7.2 B2 Mesophase 24

1.7.2.1 Variants of B2 mesophase 27

1.7.3 B3 Mesophase 28

1.7.4 B4 Mesophase 28

1.7.5 B5 Mesophase 29

1.7.5.1 Variants of B5 mesophase 30

1.7.6 B6 Mesophase 30

1.7.7 B7 Mesophase 31

1.7.7.1 Variants of B7 mesophase 33

1.7.8 B8 Mesophase 34

1.7.9 SmCG Phase 34

1.8 STRUCTURE PROPERTY RELATIONSHIP

IN BENT-CORE LIQUID CRYSTALS 34

1.8.1 Central Unit 36

1.8.2 Connecting Groups 37

1.8.3 Lateral Substitution 39

1.8.4 Terminal Chains 41

1.9 APPLICATIONS AND IMPORTANCE

OF LIQUID CRYSTALS 43

1.10 BENT-CORE LIQUID CRYSTALS –

A SURVEY 48

1.10.1 Effect of Central Unit Variation in

Mesophase 48

1.10.2 Effect of Linking or Connecting

Groups (X & Y) Variation in Mesophase 55

1.10.3 Effect of Lateral Substitution in

Mesophase 58

x

CHAPTER NO. TITLE PAGE NO.

1.10.4 Effect of Terminal Chains (R1 & R2)

Variation in Mesophase 59

1.11 SCOPE AND OBJECTIVES 66

2. EXPERIMENTAL 70

2.1 MATERIALS 70

2.2 PURIFICATION OF SOLVENTS 71

2.2.1 Benzene 71

2.2.2 Dichloromethane 71

2.2.3 Chloroform 71

2.2.4 Ethylacetate 71

2.2.5 Ethanol 72

2.2.6 Methanol 72

2.2.7 Acetone 72

2.2.8 N,N -Dimethylformamide 72

2.2.9 Thionyl Chloride 72

2.2.10 Water 73

2.3 SYNTHESIS OF KEY INTERMEDIATES 73

2.3.1 Synthesis of 4-(10-Undecenoyloxy)

biphenyl-4-carboxylic Acid (1) 73

2.3.2 Synthesis of 4-(Alkyloxy)benzoic

Acids (2a-2g) 74

2.3.3 Synthesis of 4-(4-n-Alkyloxybenzoyloxy)

benzaldehydes (3a-3g) 75

2.3.4 Synthesis of 4-(4-n-Alkyloxybenzoyloxy)

benzoic Acids (4a-4g) 76

2.3.5 Synthesis of Resorcinolmonobenzyl

ether (5) 77

xi

CHAPTER NO. TITLE PAGE NO.

2.3.6 Synthesis of 4-((3-(Benzyloxy)

phenoxy)carbonyl)phenyl-4-(alkyloxy)

benzoates (6a-6g) 77

2.3.7 Synthesis of 4-((3-Hydroxyphenoxy)

carbonyl)phenyl-4-(alkyloxy)

benzoates (7a-7g) 78

2.3.8 Synthesis of 3-(4-(4-(Alkyloxy)benzoyloxy)

benzoyloxy)phenyl-4-formyl

benzoates (8a-8g) 79

2.3.9 Synthesis of 4-(Alkyloxy)

acetanilides (9a-9g) 80

2.3.10 Synthesis of 4-(Alkyloxy)

anilines (10a-10g) 81

2.4 SYNTHESIS OF TARGET COMPOUNDS 82

2.4.1 Synthesis of 1,3-Substituted

Phenylenebis(4-(10- undecenoyloxy)-

1,1'-biphenyl-4-carboxylate)s (Ia-Ie) 82

2.4.2 Synthesis of 3-(4-(4-(alkyloxy)benzoyloxy)

benzoyloxy)phenyl-4'-(10-undecenoyloxy)

biphenyl-4-carboxylates (IIa-IIg) 83

2.4.3 Synthesis of 3-(4-(4-(alkyloxy)benzoyloxy)

benzoyloxy)phenyl-4-((4-(alkyloxy)

phenylimino)methyl)benzoates (IIIa-IIIg) 84

2.4.4 Synthesis of 3-(4-(4-(alkyloxy)benzoyloxy)

benzoyloxy)phenyl-4-((4-(decyloxy)

phenylimino)methyl)benzoates (IVa-IVg) 85

xii

CHAPTER NO. TITLE PAGE NO.

2.5 CHARACTERIZATION OF COMPOUNDS 85

2.5.1 Fourier Transform-Infrared

Spectroscopy 86

2.5.2 Nuclear Magnetic Resonance

Spectroscopy 86

2.5.3 Differential Scanning Calorimetry 87

2.5.4 Polarizing Optical Microscope 88

2.5.5 X-Ray Diffraction Measurements 89

2.5.6 Electro-Optical Investigations 90

3. RESULTS AND DISCUSSION 92

3.1 BACKGROUND OF THE STUDY 92

3.2 SYNTHESIS 94

3.2.1 Synthesis of Compounds Ia-Ie (Series I) 94

3.2.2 Synthesis of Compounds IIa-IIg (Series II) 95

3.2.3 Synthesis of Compounds IIIa-IIIg

and IVa-IVg (Series III & IV) 97

3.3 SPECTRAL TECHNIQUES OF KEY

INTERMEDIATES AND COMPOUNDS 98

3.3.1 Fourier Transform-Infrared

Spectroscopy 98

3.3.21H-Nuclear Magnetic Resonance

Spectroscopy 120

3.3.3 13

C- Nuclear Magnetic Resonance

Spectroscopy 144

xiii

CHAPTER NO. TITLE PAGE NO.

3.4 POLARIZED OPTICAL MICROSCOPY

STUDIES 165

3.4.1 Mesomorphic Property of

Compounds Ia-Ie 166

3.4.2 Mesomorphic Property of Intermediates

of Series (II) and Compounds IIa-IIg 167

3.4.3 Mesomorphic Property of

Compounds IIIa-IIIg 171

3.4.4 Mesomorphic Property of

Compounds IVa-IVg 172

3.5 DIFFERENTIAL SCANNING

CALORIMETRY 176

3.5.1 Differential Scanning Calorimetric

Study of Compounds Ia-Ie 177

3.5.2 Differential Scanning Calorimetric

Study of Compounds IIa-IIg 179

3.5.3 Differential Scanning Calorimetric

Study of Compounds IIIa-IIIg

and IVa-IVg 182

3.6 X-RAY DIFFRACTION STUDIES 187

3.6.1 X-Ray Diffraction Measurements

for Compounds IIa-IIg 187

3.6.2 X-Ray Diffraction Measurements for

Compounds IIIa-IIIg 189

3.7 ELECTRO-OPTICAL MEASUREMENT

AND SWITCHING ANALYSIS 192

3.7.1 Electro-Optical Switching Analysis

of Compounds IIa-IIg 193

xiv

CHAPTER NO. TITLE PAGE NO.

3.7.2 Electro-Optical Study and Spontaneous

Polarization Analysis of Compounds

IIIa-IIIg and IVa-IVg 196

4. CONCLUSION 207

4.1 SCOPE FOR FUTURE STUDY 211

REFERENCES 213

LIST OF PUBLICATIONS 233

VITAE 234

xv

LIST OF TABLES

TABLE NO. TITLE PAGE NO.

1.1 Current applications for liquid crystal displays 45

3.1 FT-IR spectral data of 4-n-(alkyloxy)benzoic

acids (2a-2g) 100

3.2 FT-IR spectral data of 4-(4-n-alkyloxy)benzoyloxy

benzaldehydes (3a-3g) 102

3.3 FT-IR spectral data of 4-(4-n-alkyloxybenzoyloxy)

benzoic acids (4a-4g) 103

3.4 FT-IR spectral data of 4-((3-(benzyloxy)phenoxy)

carbonyl)phenyl-4-(alkyloxy)benzoates (6a-6g) 106

3.5 FT-IR spectral data of 4-((3-hydroxyphenoxy)carbonyl)

phenyl-4-(alkyloxy)benzoates (7a-7g) 108

3.6 FT-IR spectral data of 3-(4-(4-(alkyloxy)benzoyloxy)

benzoyloxy)phenyl-4-formylbenzoates (8a-8g) 110

3.7 FT-IR spectral data of 4-(alkyloxy)

acetanilides (9a-9g) 111

3.8 FT-IR spectral data of 4-(alkyloxy)anilines (10a-10g) 113

3.9 FT-IR spectral data of compounds Ia-Ie 114

3.10 FT-IR spectral data of compounds IIa-IIg 117

3.11 FT-IR spectral data of compounds IIIa-IIIg 119

3.12 FT-IR spectral data of compounds IVa-IVg 120

3.13 1H-NMR spectral data of compounds 2a-2g 123

3.14 1H-NMR spectral data of compounds 3a-3g 124

3.15 1H-NMR spectral data of compounds 4a-4g 127

3.16 1H-NMR spectral data of compounds 6a-6g 130

3.17 1H-NMR spectral data of compounds 7a-7g 132

xvi

TABLE NO. TITLE PAGE NO.

3.18 1H-NMR spectral data of compounds 8a-8g 134

3.19 1H-NMR spectral data of 4-(alkyloxy)

acetanilides (9a-9g) 135

3.20 1H-NMR spectral data of 4-(alkyloxy)

anilines (10a-10g) 136

3.21 1H-NMR spectral data of compound Ia-Ie 138

3.22 1H-NMR spectral data of compounds IIa-IIg 140

3.23 1H-NMR spectral data of compounds IIIa-IIIg 142

3.24 1H-NMR spectral data of compounds IVa-IVg 143

3.25 13C-NMR spectral data of compounds 2a-2g 145

3.26 13C-NMR spectral data of compounds 3a-3g 147

3.27 13C-NMR spectral data of compounds 4a-4g 148

3.28 13C-NMR spectral data of compounds 6a-6g 151

3.29 13C-NMR spectral data of compounds 7a-7g 153

3.30 13C-NMR spectral data of compounds 8a-8g 155

3.31 13C-NMR spectral data of compounds 9a-9g 156

3.32 13C-NMR spectral data of compounds 10a-10g 157

3.33 13C-NMR spectral data of compounds Ia-Ie 159

3.34 13C-NMR spectral data of compounds IIa-IIg 161

3.35 13C-NMR spectral data of compounds IIIa-IIIg 162

3.36 13C-NMR spectral data of compounds IVa-IVg 164

3.37 Transition temperatures ( C) and associated

enthalpies (J/g) observed in DSC for Ia-Ie 179

3.38 Transition temperatures ( C) and associated

enthalpies (J/g) for compounds IIa-IIg 180

3.39 Transition temperatures ( C) Tm and Ti

for compounds IIa-IIe 181

xvii

TABLE NO. TITLE PAGE NO.

3.40 Transition temperatures (ºC) and associated

enthalpies (J/g) for the compounds of series III 184

3.41 Phase transition temperatures (ºC) and

associated enthalpies (J/g) for the compounds

of series IV 185

3.42 Small angle Bragg reflections (Å) and their

mesophase of compounds IIa-IIg 189

xviii

LIST OF FIGURES

FIGURE NO. TITLE PAGE NO.

1.1 Schematic representation of molecular

arrangement 2

1.2 Schematic representation of the aggregation

of amphiphiles into micelles 5

1.3 Schematic representation for classification

of thermotropic liquid crystals and its polarizing

optical microscopy image 6

1.4 (a) A general template for molecular structure of

calamitic LC and (b) an example of a calamitic LC 7

1.5 Representation of (a) nematic phase and

(b) smectic A phase 9

1.6 Representation of (a) cholesteric phase, (b) chiral

smectic C phase (SmC*) and (c) the angle in

director in subsequent layers 9

1.7 (a) General molecular structure of hexa-n-

alkanoyloxy benzenes and (b) schematic

representation of the columnar structure 11

1.8 Molecular structures of different types of

non-conventional LCs 14

1.9 Bistable switching under influence of an

electric field 16

1.10 Two types of layer organization for bent-core

molecules (a) ferroelectric and (b) antiferroelectric 17

1.11 Two types of polar switching (a) around a cone and

(b) around the molecule 18

xix

FIGURE NO. TITLE PAGE NO.

1.12 Comparison of calamitic and bent-core molecules

and their organization in the smectic layers 19

1.13 Schematic representation of the frustrated

structure of B1 mesophase 22

1.14 Proposed structures of (a) B1 and (b) B1rev 24

1.15 Pictorial representation of the geometry of a

smectic layer in the B2 (SmCPA) phase 25

1.16 Schematic representation of the arrangement of

BC molecules in racemic and chiral states of an

antiferroelectric mesophase and the corresponding

field induced ferroelectric states 27

1.17 Pictorial representation of in-plane molecular

packing in the B5 phase 29

1.18 Schematic representation of the arrangement

of BC molecules in the B6 phase 31

1.19 General scheme of a bent-shaped molecule 35

1.20 Schematic representations on usage of liquid

crystal in various fields 44

1.21 Molecular structure of target compounds

series I-IV 68

2.1 Synthesis of compound 1 73

2.2 Synthesis of compound 2a 74

2.3 Synthesis of compound 3a 75

2.4 Synthesis of compound 4a 76

2.5 Synthesis of compound 5 77

2.6 Synthesis of compound 6a 77

2.7 Synthesis of compound 7a 78

2.8 Synthesis of compounds 8a 79

xx

FIGURE NO. TITLE PAGE NO.

2.9 Synthesis of compound 9e 80

2.10 Synthesis of compounds 10e 81

2.11 Synthesis of compounds Ia-Ie 82

2.12 Synthesis of compounds IIa-IIg 83

2.13 Synthesis of compounds IIIa-IIIg 84

2.14 Synthesis of compounds IVa-IVg 85

2.15 Block diagram showing the X-ray diffraction

experimental set-up 90

2.16 Block diagram of a circuit used for the measurement

of polarization 92

3.1 Synthesis of compounds Ia-Ie (series I) 95

3.2 Synthesis of compounds IIa-IIg (series II) 96

3.3 Synthesis of compounds IIIa-IIIg & IVa-IVg

(series III & IV) 97

3.4 FT-IR spectrum of compound 1 99

3.5 FT-IR spectrum of 4-(hexyloxy)benzoic acid (2a) 100

3.6 FT-IR spectrum of 4-(4-n-heptyloxybenzoyloxy)

benzaldehyde (3b) 101

3.7 FT-IR spectrum of 4-(4-n-heptyloxybenzoyloxy)

benzoic acid (4b) 102

3.8 FT-IR spectrum of 4-(4-n-nonyloxybenzoyloxy)

benzoic acid (4d) 103

3.9 FT-IR spectrum of resorcinol monobenzylether (5) 104

3.10 FT-IR spectrum of 4-(4-n-octyloxybenzoyloxy)

phenyl monobenzylether 3-benzoate (6c) 105

3.11 FT-IR spectrum of 4-((3-(benzyloxy)phenoxy)

carbonyl)phenyl-4-(dodecyloxy) benzoate (6g) 105

xxi

FIGURE NO. TITLE PAGE NO.

3.12 FT-IR spectrum of 4-((3-hydroxyphenoxy)

carbonyl)phenyl-4-(heptyloxy)benzoate (7b) 106

3.13 FT-IR spectrum of 4-((3-hydroxyphenoxy)carbonyl)

Phenyl-4-(undecyloxy)benzoate (7f) 107

3.14 FT-IR spectrum of 4-((3-hydroxyphenoxy)

carbonyl)phenyl-4-(dodecyloxy)benzoate (7g) 107

3.15 FT-IR spectrum of 3-(4-(4-(heptyloxy)benzoyloxy)

benzoyloxy)phenyl-4-formylbenzoate (8b) 108

3.16 FT-IR spectrum of 3-(4-(4-(nonyloxy)benzoyloxy)

benzoyloxy)phenyl-4-formylbenzoate (8d) 109

3.17 FT-IR spectrum of 3-(4-(4-(dodecyloxy)

benzoyloxy) benzoyloxy)phenyl-4-formyl

benzoate (8g) 109

3.18 FT-IR spectrum of 4-(nonyloxy)acetanilide (9d) 110

3.19 FT-IR spectrum of 4-(decyloxy)acetanilide (9e) 111

3.20 FT-IR spectrum of 4-(heptyloxy)aniline (10b) 112

3.21 FT-IR spectrum of 4-(octyloxy)aniline (10c) 112

3.22 FT-IR spectrum of 4-(decyloxy)aniline (10e) 113

3.23 FT-IR spectrum of compound Ia 114

3.24 FT-IR spectrum of compound IIa 115

3.25 FT-IR spectrum of compound IIb 115

3.26 FT-IR spectrum of compound IIe 116

3.27 FT-IR spectrum of compound IIf 116

3.28 FT-IR spectrum of compound IIIf 117

3.29 FT-IR spectrum of compound IIIg 118

3.30 FT-IR spectrum of compound IVe 118

3.31 FT-IR spectrum of compound IVg 119

3.321H-NMR spectrum of compound (1) 121

xxii

FIGURE NO. TITLE PAGE NO.

3.331H-NMR spectrum of 4-(hexyloxy)benzoic acid (2a) 122

3.341H-NMR spectrum of 4-(decyloxy)benzoic acid (2e) 122

3.351H-NMR spectrum of 4-(4-n-octyloxybenzoyloxy)

benzaldehyde (3c) 124

3.361H-NMR spectrum of 4-(4-n-hexyloxybenzoyloxy)

benzoic acid (4a) 125

3.371H-NMR spectrum of 4-(4-n-heptyloxybenzoyloxy)

benzoic acid (4b) 126

3.381H-NMR spectrum of 4-(4-n-octyloxybenzoyloxy)

benzoic acid (4c) 126

3.391H-NMR spectrum of resorcinol monobenzylether (5) 127

3.401H-NMR spectrum of 4-((3-(benzyloxy)phenoxy)

carbonyl) phenyl-4-(heptyloxy)benzoate (6b) 128

3.411H-NMR spectrum of 4-((3-(benzyloxy)

phenoxy)carbonyl) phenyl-4-(octyloxy)benzoate (6c) 128

3.421H-NMR spectrum of 4-((3-(benzyloxy)phenoxy)

carbonyl) phenyl-4-(nonyloxy)benzoate (6d) 129

3.431H-NMR spectrum of 4-((3-hydroxyphenoxy)

carbonyl) phenyl-4-(heptyloxy)benzoate (7b) 129

3.441H-NMR spectrum of 4-((3-hydroxyphenoxy)

carbonyl) phenyl-4-(decyloxy)benzoate (7e) 131

3.451H-NMR spectrum of 3-(4-(4-(heptyloxy)

benzoyloxy) benzoyloxy)phenyl-4-formyl

benzoate (8b) 131

3.461H-NMR spectrum of 3-(4-(4-(undecyloxy)

benzoyloxy) benzoyloxy)phenyl-4-formyl

benzoate (8f) 133

3.471H-NMR spectrum of 4-(decyloxy)acetanilide (9e) 133

xxiii

FIGURE NO. TITLE PAGE NO.

3.481H-NMR spectrum of 4-(decyloxy)aniline (10c) 135

3.491H-NMR spectrum of compound Ia 136

3.501H-NMR spectrum of compound IIa 137

3.511H-NMR spectrum of compound IIc 139

3.521H-NMR spectrum of compound IIIe 139

3.531H-NMR spectrum of compound IVf 141

3.541H-NMR spectrum of compound IVg 141

3.5513

C-NMR spectrum of compound 1 144

3.5613

C-NMR spectrum of 4-(hexyloxy)benzoic acid (2a) 145

3.5713

C-NMR spectrum of 4-(4-n-heptyloxybenzoyloxy)

benzaldehyde (3c) 146

3.5813

C-NMR spectrum of 4-(4-n-hexyloxybenzoyloxy)

benzoic acid (4a) 146

3.5913

C-NMR spectrum of 4-(4-n-heptyloxybenzoyloxy)

benzoic acid (4b) 148

3.6013

C-NMR spectrum of resorcinolmono

benzylether (5) 149

3.6113

C-NMR spectrum of 4-((3-(benzyloxy)phenoxy)

carbonyl)phenyl 4-(heptyloxy)benzoate (6b) 149

3.6213

C-NMR spectrum of 4-((3-(benzyloxy)phenoxy)

carbonyl)phenyl-4-(octyloxy)benzoate (6c) 150

3.6313

C-NMR spectrum of 4-((3-(benzyloxy)phenoxy)

carbonyl)phenyl-4-(nonyloxy)benzoate (6d) 150

3.6413

C-NMR spectrum of 4-((3-hydroxyphenoxy)carbonyl)

phenyl-4-(octyloxy)benzoate (7c) 152

3.6513

C-NMR spectrum of 4-((3-hydroxyphenoxy)carbonyl)

phenyl-4-(decyloxy)benzoate (7e) 152

xxiv

FIGURE NO. TITLE PAGE NO.

3.6613

C-NMR spectrum of 3-(4-(4-(heptyloxy)benzoyloxy)

benzoyloxy)phenyl-4-formylbenzoate (8b) 154

3.6713

C-NMR spectrum of 3-(4-(4-(undecyloxy)benzoyloxy)

benzoyloxy)phenyl-4-formylbenzoate (8f) 154

3.6813

C-NMR spectrum of 4-(nonyloxy)acetanilide (9d) 156

3.6913

C-NMR spectrum of 4-(heptyloxy)acetanilide (10b) 157

3.7013

C-NMR spectrum of compound Ia 158

3.7113

C-NMR spectrum of compound IIa 158

3.7213

C-NMR spectrum of compound IIc 160

3.7313

C-NMR spectrum of compound IIIe 160

3.7413

C-NMR spectrum of compound IVf 163

3.7513

C-NMR spectrum of compound IVg 163

3.76 Optical photomicrographs of the textures observed

on cooling from isotropic state (A) at 88 C B1 phase

of compound Ia, (B) at 133 C B2 phase of compound

Ic and (C) at 115 C B2 phase of compound Ie 166

3.77 Electron delocalization structure of compound

(a) ester- linkage and (b) ether- linkage 168

3.78 Optical photomicrographs of the textures observed

on cooling from istropic state (A) at 112 C

B2 phase of compound IIa, (B) at 99 C B2

phase of compound IIb, (C) at 100 C B2 phase of

compound IId and (D) at 110 C B2 phase of

compound IIe 169

xxv

FIGURE NO. TITLE PAGE NO.

3.79 Optical photomicrographs of the textures observed

on cooling from isotropic state (A) at 117 C B1

phase, (B) at 113 C B1 phase, (C) at 111 C B1 phase

and (D) at 80 C mosaic texture of compound IIc 170

3.80 Optical photomicrograpy of (A) and (B) at 99 C

and 112 C of the compound IIb shows B2 phase

by cooling cycle 170

3.81 Optical photomicrographs of the textures observed

on cooling from isotropic state (A) at 120 C B1

phase of compound IIIb, (B) at 125 C B1 phase of

compound IIIc, (C) at 122 C B2 phase of compound IIId,

(D) at 128 C B2 phase of compound IIIe, (E) at 79 C B2

phase of compound IIIf and (F) at 109 C B2 phase

of compound IIIg 174

3.82 Optical photomicrographs of the textures observed

on cooling from isotropic state (A) at 121 C B1

phase of compound Iva, (B) at 100 C B1 phase of

compound IVb, (C) at 82 C B2 phase of compound IVc,

(D) at 84 C B2 phase of compound IVd, (E) at 110 C B2

phase of compound IVe and (F) at 88 C B2 phase

of compound IVf 175

3.83 Optical photomicrographs of the textures observed

on cooling from isotropic state at 88 C B2 phase

of compound IVg 176

3.84 DSC thermograms traces of compounds Ia-Ie 178

3.85 Plot of transition temperature as a function of various

compounds Ia-Ie 178

xxvi

FIGURE NO. TITLE PAGE NO.

3.86 DSC thermogram of compound IIc 180

3.87 Plot of transition temperature as a function of spacer

length for compounds IIa-IIg 181

3.88 DSC thermogram traces of compounds IIIa-IIg 182

3.89 DSC thermogram traces of compounds IVa-IVg 183

3.90 Variation of transition temperatures with terminal

chain length on cooling the compounds IIIa-IIIg 186

3.91 Variation of the transition temperatures with terminal

chain length on cooling the compounds IVa-IVg 186

3.92 Variable temperatures XRD patterns for B1

phase of compound IIc at 90 °C 188

3.93 Variable temperature XRD patterns for the B2

phase of compound IIe at 100 °C 188

3.94 XRD pattern of an un-oriented sample in the

SmCPA (B2) phase of compound IIIe at 125 °C 190

3.95 X-Ray diffraction pattern of an un-oriented sample

in the B1 phase of compound IVa at 120 °C 191

3.96 (a) XRD intensity against angle profile at 116 °C

and (b) optical photomicrographs in the B2 phase

of compound IVb at 116 °C 192

3.97 Switching current behavior of the compound IIa

in homogeneously aligned cell with 5

at 20 Hz of frequency and the amplitude of 20 Vp-p 193

3.98 Switching current behavior of the compound IIb in

homogeneously aligned cell with 5

at 20 Hz of frequency and the amplitude of 20 Vp-p 194

xxvii

FIGURE NO. TITLE PAGE NO.

3.99 Switching current behavior of the compound IIe in

homogeneously aligned cell with 5

at 20 Hz of frequency and the amplitude of 20 Vp-p 194

3.100 Switching current behavior of the compound IIf

in homogeneously aligned cell with 5

at 20 Hz of frequency and the amplitude of 20 Vp-p 195

3.101 Magnitudes of the spontaneous polarization plotted

as a function of temperature for compounds IIa-IIg 196

3.102 Optical photomicrographs in the B2 phase of

compound IIIe at 115 °C (a) before applying electric

field (b) after the treatment with low frequency

electric field 197

3.103 Optical photomicrographs in the B2 phase of

compound IIIe under the application of DC

electric fields, (a) +25 V, (b) -25 V, (c) +20 V

(d) -20 V, (e) +15 V and (f) -15 V at 115 °C 198

3.104 POM textures in the B2 phase at 88 °C of compound

IVg (A) before application of electric field and (B) after

the treatment with low frequency electric field 198

3.105 Texture of the field-induced SmCPA of

compound IVd (a) +30 V (b) 0 V and (c) -30 V 200

3.106 Current responses to a triangular voltage

(55 V, 200 Hz) in the B2 phase of compound IIId

showing the antiferroelectric characteristics at 120 °C 201

3.107 Current responses to a triangular voltage

(55 V, 200 Hz) in the B2 phase of compound IIIe

showing the antiferroelectric characteristics at

125 °C 201

xxviii

FIGURE NO. TITLE PAGE NO.

3.108 Current responses to a triangular voltage (55 V, 200 Hz)

in the B2 phase of compound IIIf showing the

antiferroelectric characteristics at 122 °C 202

3.109 Current responses to a triangular voltage (55 V, 200 Hz)

in the B2 phase of compound IIIg showing the

antiferroelectric characteristics at 98 °C 202

3.110 Current responses to a triangular voltage

(55 V, 200 Hz) in the B2 phase of compound IVc

showing the antiferroelectric characteristics at 128 °C 203

3.111 Current responses to a triangular voltage (55 V, 200 Hz)

in the B2 phase of compound IVd showing the

antiferroelectric characteristics at 125 °C 203

3.112 Current responses to a triangular voltage (55 V, 200 Hz)

in the B2 phase of compound IVe showing the

antiferroelectric characteristics at 120 °C 204

3.113 Current responses to a triangular voltage (55 V, 200 Hz)

in the B2 phase of compound IVf showing the

antiferroelectric characteristics at 110 °C 204

3.114 Current responses to a triangular voltage

(55 V, 200 Hz) in the B2 phase of compound IVg

showing the antiferroelectric characteristics

at 115 °C 205

3.115 Temperature dependence of the measured

spontaneous polarization in the SmCPA phase of

compound IIIe 206

xxix

LIST OF SYMBOLS AND ABBREVIATIONS

H - Enthalpy

T - Mesophase duration

- Micro meter

C - Degree centigrade

Å - Angstrom

a.u - Arbitrary unit

AC - Alternate current

AF - Antiferroelectric

AFLCD - Antiferroelectric liquid crystal display

b.p - boiling point

BP - Blue phase

cm-1 - per centimetre

Col - Columnar

Colr - Rectangular columnar

CRT - Cathode ray tube

CU - Central unit

DC - Direct current

DCC - N,N-dicyclohexylcarbodiimide

DMAP - 4-(dimethylamino)pyridine

DSC - Differential scanning calorimetry

F - Ferroelectric

FLCD - Ferroelectric liquid crystals

FT-IR - Fourier transform infrared spectroscopy

g - Gram

h - Hour

HCl - Hydrochloric acid

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Hz - Herz

ITO - Indium tin oxide

J/g - Jules per gram

k - Kilo ohm

K2CO3 - Potassium carbonate

KI - Potassium iodide

LC - Liquid crystal

LCDs - Liquid crystal displays

lit. - Litre

mg - Milligram

min - Minute

mmol - Milli mole

mol - Mole

n - n- Number of methylene unit

N - nematic

N* - Chiral nematic

NaOH - Sodium hydroxide solution

NMR - Nuclear Magnetic Resonance

OLCs - Oligomeric liquid crystals

Pd/C - Palladium carbon

POM - Polarizing Optical Microscope

ppm - Parts per million

Ps - Spontaneous polarization

RC1 and RC2 - Rigid cores

S - Second

SmA - Smectic A

SmC - Smectic C

SmC* - Chiral smectic C

SmC* - Chiral smectic C phase

TGB - Twist grain boundary

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THF - Tetrahydrofuran

Ti - Isotropic temperature

Tm - Melting transition temperature

V - Voltage

Vp-p - Volt peak to peak

XRD - X-ray diffraction