臺灣博碩士論文加值系統

本研究主要是以 (S)-lactic acid 與2-methylsulfanyl-1-ethanol合成出(S)-2-(metylsulfanyl)ethyl 2-hydroxypropanoate旋光起始物，以及用(S)-propylene oxide與2-methylsulfanyl-1-ethano合成出(S)-[1-methyl-2-(2’-methylsulfanylethoxy)]ethanol旋光起始物。並以這兩種起始物設計及合成三系列旋光性液晶材料，分別探討（i）非旋光末端烷鏈長度’m’及（ii）在硬核中心導入氟側邊取代基對於液晶相及物理光電特性的影響，以建立分子結構與旋光液晶相的關係。
第一系列液晶材料MSEmBCPP (m=8-12) 中具有SmA*及誘電性SmC*液晶相。誘電性SmC*相的最大的自發性極化值在85 nC/cm2。量測此誘電性SmC*液晶相的光電應答性質時發現：在特定的頻率及溫度下呈現典型誘電性遲滯或無遲滯之V形轉換行為。
第二系列材料MMSEEmCB(m=7-12) 中在非旋光烷鏈對於層列型液晶相有重要的影響。當m=7時呈現SmA*、SmCA*和SmX* 液晶相。當m=8-12增加了SmC*相的出現，但當m=10-12時反誘電性液晶相SmCA*消失；當m=11-12時SmX*相消失。本系列最大的自發性極化值在37.76 nC cm-2，而最大的傾斜角為29.5o。
第三部分在苯環第二含氟測邊取邊代液晶材料MMSEEmBC2F(m=7–10) 和苯環第三含氟測邊代液晶材料MMSEEmBC3F(m=7–10)中均呈現SmA*和SmC*相，而在MMSEE7BC2F 和 MMSEE8BC3F兩個材料出現反誘電性液晶相SmCA*。此結果顯示出在硬核中心的苯環上導入氟側邊取代基會壓制SmCA*和SmX*相的生成，降低相轉移溫度，熔點及澄清點的溫度。比較含氟測邊取代及不含氟測邊取代的材料之自發性極化值，可以發現Ps值的大小依順序為MSEmBCPP > MMSEE7BC2F > MMSEE8BC3F，顯示氟測邊取代可降低自發性極化值，而其中第三含氟測邊取邊代效應又比第二含氟測邊代的壓抑效應較高。
綜合以上結果得知：以(S)-2-(metylsulfanyl)ethyl 2-hydroxypropanoate 所衍申之液晶材料具有寬廣的誘電性液晶相SmC*。而以(S)-[1-methyl-2-(2’-methylsulfanylethoxy)]ethanol所衍申之液晶材料具有反誘電性SmCA*液晶相。氟測邊取代可降低相轉移溫度但不利於反誘電性液晶相之形成。

The primary of this research work was an attempt to elucidate the correlation between structure and property in the chiral smectic liquid crystals. Thus, two new chiral moieties, (S)-2-(metylsulfanyl)ethyl 2-hydroxypropanoate prepared by reacting (S)-lactic acid with 2-methylsulfanyl-1-ethanol, and (S)-[1-methyl-2-(2’-methylsulfanylethoxy)]ethanol prepared by reacting (S)-propylene oxide with 2-methylsulfanyl-1-ethanol under basic condition, were designed and synthesized, and three series of chiral liquid crystal compounds were subsequently prepared for the mesomorphic and physical studies. The target compounds were modified independently by (i) the non-chiral peripheral methylene chain length ‘m’ and (ii) the lateral substitution group in the core.
In first series of chiral materials, MSEmBCPP(m=8-12), all materials displayed enantiotropic mesophases of the SmA*, and SmC* phases. The maximum magnitude of spontaneous polarization (Ps) for materials was around 85nC/cm2. The electro-optical response in the series of chiral materials in the SmC* phase displayed typical ferroelectric hysteresis loop or hysteresis-free, V-shaped switching property upon various applied frequencies and temperatures.
In second series of chiral materials, MMSEEmCB(m=8-12), the formation of smectic phases are significantly depended of the achiral alkyl chain length. For example, material at m=7 displayed SmA*, SmCA* and SmX phases, while materials at m=8-12 display an additional SmC* phase but at m=10-12 the SmCA* phase and at m=11-12 the SmX* were suppressed. The maximum Ps value was observed to be 37.76 nC cm-2, and the maximum tilt angle reached 29.5o.
In the third series of materials, the results obtained from MMSEEmBC2F(m=7–10) with lateral 2-fluoro substitution and MMSEEmBC2F(m=7–10) with 3-fluoro show that all materials display SmA* and SmC* phases. The antiferroelectric SmCA* phase only occurred in two materials, MMSEE7BC2F and MMSEE8BC3F. The results also indicate that lateral fluoro-substituent in the phenyl ring of the materials could depress the formation of higher ordered smectic phases, especially the SmCA* and SmX* phases, lowering the transition temperatures, melting points, clearing points. The measured Ps values, as compared fluoro-substituted materials to non-substtuted materials, have the order of MSEmBCPP > MMSEE7BC2F > MMSEE8BC3F, suggesting that fluoro-substituents depress the Ps values in which 3-fluoro-substituent has more effect than 2-fluoro-substituent.
In conclusion, the results indicated that the chiral materials derived from (S)-2-(metylsulfanyl)ethyl 2-hydroxypropanoate are favorable for the formation of the wide temperature range of the ferroelectric phase, while that from (S)-1-methyl-2-(2’-methylsulphanylethoxy)ethanol are favorable for the formation of antiferroelectic phase. Fluoro-substituents could decrease the transition temperatures but suppress the formation of antiferroelectric phase.

CHINESE ABSTRACT I
ENGLISH ABSTRACT III
ACKNOWLEDGEMENTS VI
TABLE OF CONTENTS VII
LIST OF SCHEME XII
LIST OF TABLES XIII
LIST OF FIGURES XIV
CHAPTER 1 INTRODUCTION 1
1.1. Overview 2
1.2. Chiral nematic, N*, (or Cholesteric, Ch) liquid crystals 2
1.3. Chiral smectic phases 6
1.3.1 Chiral smectic A phase 6
1.3.2. Chiral smectic C phase (ferroelectric phase) 6
1.3.3 Antiferroelectric phase 11
1.4. Motivation of study 20
PART 1. Synthesis and properties of new chiral liquid crystals derived from (S)-lactic acid with 2-(methylsulfanyl)-1-ethanol 26
ABSTRACT 27
CHAPTER 1INTRODUCTION 28
CHAPTER 2 30
EXPERIMENTAL 30
2.1. Characterization of materials 30
2.2. Preparation of materials 31
2.2.1. 4-(4-Alkyloxyphenyl)benzoic acids, compound 1(m=8–12) 33
2.2.2. 4-Methoxycarbonyloxybenzoic acid, compound 2 33
2.2.3. (S)-2-(Metylsulfanyl)ethyl 2-hydroxypropanoate, compound 3 34
2.2.4. (R)-1-Hydroxy-1-methyl-2-[2-(methylsulfanyl)ethoxy]-2-oxoethyl 4-[(methoxycarbonyl)oxy]benzoate, compound 4 34
2.2.5. (R)-1-Methyl-2-[2-(methylsulfanyl)ethoxy]-2-oxoethyl 4-hydroxybenzoate, compound 5 35
2.2.6. 2-(Methylsulfanyl)ethyl (R)-2-[4-(4’-alkyloxybiphenylcarnbonyloxy)-
phenylcarbonyloxy]propionate, MSEmBCPP(m=8-12) 36
CHAPTER 3 37
RESULTS AND DISCUSSION 37
CHAPTER 4 46
SUMMARY 46
REFERENCES 47
PART 2. Synthesis and properties of ferroelelctric and antiferroelectric liquid crystals derived from (S)-[1-methyl-2-(2’-methylsulfanylethoxy)]ethanol 49
ABSTRACT 50
CHAPTER 1 INTRODUCTION 51
CHAPTER 2 EXPERIMENTAL 52
2.1. Characterization of materials 52
2.2. Preparation of materials 53
2.2.1. Synthesis of 4-(4-alkyloxyphenyl)benzoic acids, I-1(m=8~12) 55
2.2.2. Synthesis of 4-methoxycarbonyloxybenzoic acid, I-2 55
2.2.4. Synthesis of 1-methyl-2-(methylsulfanyl)ethyl (R)-2-[4-(methoxycarbonyloxy)-
benzoyloxy]propionate, I-4. 56
2.2.3. Synthesis of (S)-[1-methyl-2-(2’-methylsulfanylethoxy)]ethanol, I-3 56
2.2.5. Synthesis of 1-methyl-2-(methylsulfanyl)ethyl (R)-2-(4-hydroxybenzoyloxy)-
propionate, I-5 57
2.2.6. Synthesis of (R)-[1-methyl-2-(2’-methylsulfanylethoxy)]ethyl 4-(4’-alkoxybiphenyl
-1-carboxyloxy)benzoates, I-6, MMSEEmCB(m=7-12) 59
CHAPTER 3 RESULTS AND DISCUSSION 60
3.1. Mesophase properties 60
3.2. Electro-optical studies 60
CHAPTER 4 SUMMARY 70
REFERENCES 71
PART 3 The effect of lateral fluoro substituents on the chiral liquid crystal materials derived from (S)-1-methyl-2-(2’-methylsulphanylethoxy)Ethanol 72
ABSTRACT 73
CHAPTER 1 74
INTRODUCTION 74
CHAPTER 2 76
EXPERIMENTAL 76
2.1. Characterization of materials 76
2.2. Preparation of materials 77
2.2.1. 2-Fluoro-4-hydroxybenzoic acid, I-2 79
2.2.2. Synthesis of 3-fluoro-4-hydroxybenzoic acid, I-3 79
2.2.3. Synthesis of 2-fluoro4-methoxycarbonyloxybenzoic acid, I-4 80
2.2.4. Synthesis of 3-fluoro-4-methoxycarbonyloxybenzoic acid, I-5 80
2.2.5. Synthesis of (S)-[1-methyl-2-(2-methylsulphanylethoxy)]ethanol, I-6 81
2.2.6. Synthesis of (R)-[1-methyl-2-(2-methylsulphanylethoxy)]ethyl 4-(methoxycarbonyloxy)-2-fluorobenzoate, I-7 81
2.2.7. Synthesis of (R)-[1-methyl-2-(29-methylsulphanylethoxy)]ethyl 4-(methoxycarbonyloxy)-3-fluorobenzoate, I-8. 82
2.2.8. Synthesis of (R)-1-methyl-2-(methylsulphanyl)ethyl 4-hydroxy-2-fluorobenzoate, I-9. 82
2.2.9. Synthesis of (R)-1-methyl-2-(methylsulphanyl)ethyl 4-hydroxy-2-fluorobenzoate, I-10. 83
2.2.10. Synthesis of (R)-[1-methyl-2-(2-methylsulfanylethoxy)]ethyl 4-(4’-alkoxybiphenyl-1-carboxyloxy)-2-fluorobenzoates, MMSEEmBC2F(m=7–10) 84
2.2.11. Synthesis of (R)-[1-methyl-2-(2-methylsulphanylethoxy)]ethyl 4-(4-alkoxybiphenyl-1-carboxyloxy)-3-fluorobenzoates, MMSEEmBC3FB (m=7–10) 85
CHAPTER 3 86
RESULTS AND DISCUSSION 86
3.1. Mesophase properties 86
3.2. Electro-optical studies 87
CHAPTER 4 97
SUMMARY 97
REFERENCES 98
CONCLUSIONS 100

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