臺灣博碩士論文加值系統

本研究主要在探討液晶分子結構對於TGB液晶相及旋光性液晶相性質的影響。因此，本實驗設計以(S)-2-(6-methoxy-2-naphthyl)propionic acid 合成三個系列的旋光性液晶材料，並分別探討(i)旋光支鏈長度’q’以及(ii)第二旋光中心和(iii)非旋光末端烷鏈長度’m’對於液晶相與物理光電特性的影響。
實驗結果顯示：在±S-C12-q第一系列中當q=0時，出現SmA*-SmC*的液晶相順序；在q=1的時候，具有N*-TGBA*-TGBC*的液晶相順序；而在q=2,3，則出現N*-TGBA*-SmA*-SmC*的液晶相順序。在第二系列RS-Cm-1 (m=8-12)中，所有的材料都具有SmA*和SmC*液晶相，而在較短的非旋光末端烷鏈材料則額外出現N*(m=8,9)和TGBA*(m=8)液晶相。第三系列SS-Cm-1 (m=8-12)大多呈現N*-TGBA*-SmA*-SmC*液晶相順序，除了m=10額外出現了BPII和BPIII液晶相。
三系列液晶化合物±S-C12-q (q=0-3)， RS-Cm-1 (m=9-11)和SS-Cm-1 (m=9-11)的自發性極化值最大值介於1.2-23nC/cm2，而在±S-C12-q (q=0-3), RS-Cm-1 (m=10-12)與SS-Cm-1 (m=10-12)中，傾斜角最大值介於29-45o。另外，由光電應答量測中顯示在±S-C12-2的材料中可以在SmC*液晶相下得到V型無閥轉換行為。
綜合以上結果可知旋光末端支鏈可以幫助TGB液晶相的生成，以及(S, S) 同分異構物在挫敗液晶相中比(R, S) 同分異構物具有較好的熱穩定性。在自發性極化值與傾斜角方面，(S, S)同分異構物都比(R, S)同分異構物來的大。

The purpose of this research works was an attempt to elucidate the effect of molecular structure on the stability of TGB phase and mesomorphic properties of the chiral liquid crystals. A homologous series of chiral materials derived from (S)-2-(6-methoxy-2-naphthyl)propionic acid has been successfully synthesized. The target compounds were modified in dependently by (i) the chiral branch chain length ‘q’, (ii) the second chiral center and (iii) the nonchiral peripheral alkyl chain length ‘m’.
Compound ±S-C12-q (q=0) displayed mesophase of SmA*-SmC*, compound ±S-C12-q (q=1) exhibited the N*-TGBA*-TGBC*, and others compounds ±S-C12-q (q=2, 3) showed the phase sequence of N*-TGBA*-SmA*-SmC*. Compounds RS-Cm-1 (m-8-12) all exhibited the SmA* and SmC* phases, but at shorter alkyl chain compounds RS-Cm-1 (m=8, 9) displayed additional N* phase and compound RS-Cm-1 (m=8) displayed TGBA* phase. Compounds SS-Cm-1 (m=8-12) showed the mesophases sequence of N*-TGBA*-SmA*-SmC*. Compound SS-Cm-1 (m=10) displayed additional BPII and BPIII phases.
The maximum magnitudes of spontaneous polarization (Ps values) for the chiral materials ±S-C12-q (q=0-3), RS-Cm-1 (m=9-11) and SS-Cm-1 (m=9-11) were obtain in the range of 1.2-23nC/cm2 and the maximum optical tilt angle values of compounds ±S-C12-q (q=0-3), RS-Cm-1 (m=10-12) and SS-Cm-1 (m=10-12) were between 29-45o. The electro-optical response demonstrated that material ±S-C12-2 displayed thresholdless V-shaped switching in the SmC* phase.
In conclusion, the results indicated that the branched chain of the terminal group may help the TGB phase formation, and the (S, S)-isomers had better thermal stability of frustrated phase than (R, S)-isomers. The spontaneous polarization values of (S, S)-isomers were higher than (R, S)-isomers, and the (S, S)-isomers had higher optical tilt angles than (R, S)-isomer.

ACKNOWLEDGMENTS……………………………………………………………………………iii
ENGLISH ABSTRACT……………………………………………………………………………iv
中文摘要…………………………………………………………………………………………vi
TABLE OF CONTENTS……………………………………………………………………………v
LIST OF SCHEME………………………………………………………………………………ix
LIST OF TABLES…………………………………………………………………………………x
LIST OF FIGURES………………………………………………………………………………xi
CHAPTER 1
INTRODUCTION.…………………………………………………………………………………1
1.1 Overview……………………………………………………………………………………1
1.2 Cholesteric (Ch) or chiral nematic (N*) phase……………………………3
1.3 Chiral smectic phase…………………………………………………………………5
1.3.1 Smectic A* phase……………………………………………………………………5
1.3.2 Chiral smectic C phase (ferroelectric phase)…………………………7
1.4 Frustrated phases……………………………………………………………………12
1.4.1 Blue phase……………………………………………………………………………12
1.4.2 Twist grain boundary phases…………………………………………………15
1.4.3 The TGBA* phase……………………………………………………………………16
1.4.4 The TGBC* phase……………………………………………………………………18
1.5 The purpose of this study…………………………………………………………20
CHAPTER 2
EXPERIMENTAL…………………………………………………………………………………23
2.1 Preparation of materials…………………………………………………………23
2.1.1 Synthesis of 4-(4’-alkoxyphenyl)benzoic acid, CmCOOH…………25
2.1.2 Synthesis of 4-(4’-alkoxyphenyl)benzyl alcohols, CmCH2OH……25
2.1.3 Synthesis of alkylbutyl (±, R, or S, S)-2-(6-methoxy-2-naphthyl)propionates, ±S-CH-q -CH, RS-CH-1 and SS-CH-1……………26
2.1.4 Synthesis of alkylbutyl (±, R, or S, S)-2-(6-hydroxy-2-naphthyl)propionates,
±S-OH-q, RS-OH-1 and SS-OH-1…………………………………………………………27
2.1.5 Synthesis of alkylbutyl (±, R, or S, S)-2-{6-[4-(4’-alkyloxyphenyl)benzyloxy] -2-naphthyl}propionates, ±S-C12-q, RS-Cm-1 and SS-Cm-1……………………………………………………………………………………28
2.2 Physical properties…………………………………………………………………29
2.2.1 Chemical structure identification………………………………………29
2.2.2 Mesophases identification……………………………………………………29
2.2.3 Measurement of switching behavior………………………………………30
2.2.4 Measurement of spontaneous polarization………………………………31
2.2.5 Dielectric constant measurement……………………………………………34
2.2.6 Optical tilt angle………………………………………………………………34
2.2.7 Optical response measurement………………………………………………35
CHAPTER 3
RESULTS AND DISSCUSSION…………………………………………………………………37
3.1 Chemical structure identifications……………………………………………37
3.2 The effect of branch chain length in chiral group of the molecular; ±S-C12-q (q=0-3)……………………………………………………………40
3.2.1 Optical microscopy studies of ±S-C12-q (q=0-3)……………………45
3.2.2 Differential scanning calorimetry (DSC) of ±S-C12-q (q=0-3)…46
3.2.3 Switching current behavior of ±S-C12-q (q=0-3)……………………52
3.2.4 Spontaneous polarization (Ps) of ±S-C12-q (q=0-3)………………52
3.2.5 Dielectric properties of ±S-C12-q (q=0-3)……………………………55
3.2.6 Optical tilt angle (θ) of ±S-C12-q (q=0-3)…………………………55
3.2.7 Electro-optical responses of ±S-C12-2…………………………………56
3.3 The effect of achiral alkyl chain for compounds; RS-Cm-1; (m=8-12)…………………………………………………………………………………………………61
3.3.1 Optical microscopy studies of RS-Cm-1 (m=8-12)……………………61
3.3.2 Differential scanning calorimetry (DSC) of RS-Cm-1 (m=8-12)……………………………………………………………………………………………………62
3.3.3 Switching current behavior of RS-Cm-1 (m=8-12)……………………68
3.3.4 Spontaneous polarization (Ps) of RS-Cm-1 (m=9-11)………………68
3.3.5 Dielectric properties of RS-Cm-1 (m=8-12)……………………………71
3.3.6 Optical tilt angle (θ) of RS-Cm-1 (m=10-12)…………………………71
3.4 The effect of achiral alkyl chain for compounds; SS-Cm-1 (m=8-12)……………………………………………………………………………………………………75
3.4.1 Optical microscopy studies of SS-Cm-1 (m=8-12)……………………75
3.4.2 Differential scanning calorimetry (DSC) of SS-Cm-1 (m=8-12)…76
3.4.3 Switching current behavior of SS-Cm-1 (m=8-12)……………………83
3.4.4 Spontaneous polarization (Ps) of SS-Cm-1 (m=9-11)………………83
3.4.5 Dielectric properties of SS-Cm-1 (m=8-12)……………………………86
3.4.6 Optical tilt angle (θ) of SS-Cm-1 (m=10-12)…………………………86
3.5 A comparison of mesomorphic properties for the compounds ±S-C12-q (q=1), RS-Cm-1 (m=12) and SS-Cm-1 (m=12)……………………………………90
3.6 A comparison of spontaneous polarization for the compounds ±S-C12-q (q=1), RS-Cm-1 (m=12) and SS-Cm-1 (m=12)………………………………90
3.7 A comparison of tilt angle for the compounds ±S-C12-q (q=1), RS-Cm-1 (m=12) and SS-Cm-1 (m=12)………………………………………………………91
CHAPTER 4
CONCLUSIONS……………………………………………………………………………………96
REFERENCES………………………………………………………………………………………98

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