臺灣博碩士論文加值系統

本研究主要是在說明旋光性層相液晶其結構與性質之間的關係，以 (R)-(+)-2-(4-hydroxyphenoxy)propanoic acid 為起始物合成一系列旋光性液晶材料，並分別探討(i)非旋光末端烷鏈長度及(ii)旋光末端醚氧烷鏈長度(iii)旋光中心與苯環之連接基為醚基時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。
實驗結果顯示：三系列液晶材料 I(m=8~12, n=1), II(m=8~12, n=3), III(m=8~12, n=4)都具有寬廣溫度範圍之SmA*與SmC*兩種液晶相，且大部分液晶材料存在SmX*液晶相。隨著非旋光末端烷鏈長度’m’的增加，發現大部分液晶相的溫度範圍會隨著降低。換句話說就是澄清點隨著降低、結晶點隨著升高。當旋光末端醚烷鏈長度’n’增加，會使 SmC* 與 SmX* 液晶相的溫度範圍降低。
三系列化合物在SmC*液晶相進行光電的量測時顯示在改變溫度和頻率下可得到遲滯或V型無遲滯行為。其自發極化值之最大值介於34.20~124.32 nC/cm2，隨著末端醚烷鏈長’n’的增加，自發極化值的最大值會隨之降低。其傾斜角的最大值範圍介於14.5o~31.5o之間，隨著末端醚烷鏈長’n’的增加，傾斜角會隨之變小。
綜合以上結果得知：由(R)-(+)-2-(4-hydroxyphenoxy)propanoic acid衍生之醚氧末端烷鏈液晶材料具有誘電性液晶相並且在光電行為量測產生V型無遲滯行為。

The primary of this research work was an attempt to elucidate the structure-property correlation in the chiral smectic liquid crystal. A homologous series of chiral materials derived from (R)-(+)-2-(4-hydroxyphenoxy)propanoic acid, has been successfully synthesized and the structures-property relationship investigated in the chiral liquid crystal system. The target compounds were modified independently by the (i) nonchiral peripheral chain length, (ii) the chiral tailed ether alkyl chain length (iii) the linking groups; where the chiral group is connected to the rigid core by ether group.
Chiral materials of three series Ⅰ(m=8~12, n=1), Ⅱ(m=8~12, n=3), and Ⅲ(m=8~12, n=4) displayed enantiotropic mesophases of the SmA* and SmC* phases and most of them have SmX* phase. In compounds Ⅲ(m=8~12, n=4) the temperature range of the mesophase decrease as the nonchiral chain length was increased. It means that the clearing point decreased and the crystal point increased. When the chiral tailed ether alkyl chain length ‘n’ was increased, the temperature range of the SmC* phase and SmX* were decreased.
The electro-optical response in the series of chiral materials in the SmC* phase displayed typical ferroelectric hysteresis loop or hysteresis-free, V-shaped switch property upon various applied frequencies and temperatures. The maximum Ps values of Ⅰ(m=9~11, n=1), Ⅱ(m=9~11, n=3), and Ⅲ(m=8~10, n=4) vary from 34.20~124.32 nC/cm2. Ps value decreases with increasing of the chiral tailed chain length ’n’. The maximum tilt angles of Ⅰ(m=9~11, n=1), Ⅱ(m=9~11, n=3), and Ⅲ(m=8~10, n=4) were in the range of 14.5o~31.5o. There is also a decreasing tendency of tilt angle as increasing chiral chain length.
In conclusion, the results indicated that the chiral tailed ether alkyl chain materials derived from (R)-(+)-2-(4-hydroxyphenoxy)propanoic acid are favorable for the formation of the ferroelectric phase. V-shaped switching behavior achieved in the SmC* phase of the three series of chiral compounds.

CHINESE ABSTRACT------------------------------------------------------------Ⅲ
ENGLISH ABSTRACT------------------------------------------------------------Ⅳ
ACKNOWLEDGMENTS-------------------------------------------------------------Ⅵ
TABLE OF CONTENTS-----------------------------------------------------------Ⅶ
LIST OF SCHEME--------------------------------------------------------------Ⅹ
LIST OF TABLES-------------------------------------------------------------ⅩⅠ
LIST OF FIGURES------------------------------------------------------------ⅩⅡ
CHAPTER 1--------------------------------------------------------------------1
INTRODUCTION-----------------------------------------------------------------1
1.1 Overview-----------------------------------------------------------------1
1.2 Chiral Smectic Phases----------------------------------------------------1
1.2.1 Chiral Smectic A Phase-------------------------------------------------1
1.2.2 Chiral Smectic C Phase (Ferroelectric phase)---------------------------3
1.3 Motivation of Study------------------------------------------------------9
CHAPTER 2-------------------------------------------------------------------12
EXPERIMENTAL----------------------------------------------------------------12
2.1 Preparation of Materials------------------------------------------------12
2.1.1 Synthesis of 4-(4’-alkoxybiphenyl)benzoic acids, I-1-----------------12
2.1.2 Synthesis of (R)-(+)-2-[4-(benzyloxy)phenoxy]propanoic acid, I-2------13
2.1.3 Synthesis of 2-alkyloxyethyl (R)-(+)-2-[4-(benzyloxy)phenoxy]propionate, I-3, II-3, III-3------------------------------------------------------------13
2.1.4 Synthesis of 2-alkyloxyethyl (R)-(+)-2-(4-hydroxyphenoxy) propionate, I-4, II-4, III-4--------------------------------------------------------------15
2.1.5 Synthesis of 2-alkyloxyethyl (R)-(+)-2-[4-(4’-alkyloxyphenylbenzyloxy)phenoxy] propionate, I-5, II-5, III-5---------------------------------------16
2.2 Physical properties-----------------------------------------------------17
2.2.1 Mesophase identification----------------------------------------------17
2.2.2 Preparation of homogenous cells---------------------------------------17
2.2.3 Alignment of liquid crystals in SSFLC cells---------------------------18
2.2.4 Spontaneous polarization measurement----------------------------------18
2.2.5 Optical response measurement------------------------------------------18
2.2.6 The optical tilt angle------------------------------------------------19
CHAPTER 3-------------------------------------------------------------------21
RESULTS AND DISCUSSION------------------------------------------------------21
3.1 Chemical structure identification---------------------------------------21
3.2 Mesomorphic properties of compounds I (m=8~12)：the effect of peripheral chain length----------------------------------------------------------------24
3.2.1 Transition temperatures and optical microscopic studies---------------24
3.2.2 Switching behavior----------------------------------------------------30
3.2.3 Spontaneous polarization (Ps)-----------------------------------------36
3.2.4 Electro-optical responses---------------------------------------------36
3.2.5 The optical tilt angle------------------------------------------------39
3.3 The effect of peripheral chain length; II (m=8~12)----------------------39
3.3.1 Transition temperatures and optical microscopic studies---------------39
3.3.2 Switching behavior----------------------------------------------------45
3.3.3 Spontaneous polarization (Ps)-----------------------------------------45
3.3.4 Electro-optical responses---------------------------------------------45
3.3.5 The optical tilt angle------------------------------------------------49
3.4 The effect of peripheral chain length; III (m=8~12)---------------------49
3.4.1 Transition temperatures and optical microscopic studies---------------53
3.4.2 Switching behavior----------------------------------------------------56
3.4.3 Spontaneous polarization (Ps)-----------------------------------------56
3.4.4 Electro-optical responses---------------------------------------------60
3.4.5 The optical tilt angle------------------------------------------------60
3.5 A comparison of in mesomorphic properties, spontaneous polarization, and tilt angle for the compounds I, II, III (m=10)------------------------------64
3.5.1 Mesomorphic properties------------------------------------------------64
3.5.2 Spontaneous polarization (Ps)-----------------------------------------64
3.5.3 The optical tilt angle------------------------------------------------64
CHAPTER 4-------------------------------------------------------------------69
CONCLUSIONS-----------------------------------------------------------------69
REFERENCES------------------------------------------------------------------70

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