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研究生:游逸群
研究生(外文):Yi-Chun Yu
論文名稱:探討具氯化甲烷旋光基的旋光性液晶材料的液晶相及光電性質
論文名稱(外文):Study on the Mesophases and Electro-optical Properties of Chiral Liquid Crystals Derived from Chloromethyl Substituent Positioned at Asymmetric Carbon
指導教授:吳勛隆
指導教授(外文):Shune-Long Wu
學位類別:碩士
校院名稱:大同大學
系所名稱:化學工程學系(所)
學門:工程學門
學類:化學工程學類
論文種類:學術論文
論文出版年:2008
畢業學年度:96
語文別:英文
論文頁數:116
中文關鍵詞:新型旋光性材料誘電性液晶V型光電應答行為
外文關鍵詞:ferroelectric liquid crystalV-shaped electro-optical responsenew chiral material
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影響誘電性SmC* 液晶相其性質的因素有很多,像是旋光中心、硬核構造、連接基、末端烷鏈的長度和光學純度等等。本研究的目的是為進一步了解分子結構與液晶相性質的關係。
因此,本實驗以含有氯化甲烷基的(S)-1-alkyloxy-3-chloro-2-propanols為起始物,合成六系列新型含氯化甲烷基旋光中心的液晶材料來分別探討(i)旋光中心的側邊取代導入氯化甲烷基,觀察是否有其他液晶相的生成(ii)改變液晶分子旋光及非旋光末端柔軟鏈長度(n, m),觀察其液晶相變化(iii)改變硬核中心的結構,探討其對物理性質的影響。
實驗結果顯示: 除了IV(m=8)和VI(m=8) 僅有SmA*液晶相的生成,所有化合物都具有SmA*及SmC*液晶相。六系列化合物I(m=8-12, n=3), II(m=8-12, n=4), III(m=8-12, n=5), IV(m=9-12, n=3), V(m=8-12, n=4)和VI(m=9-12, n=5)的Ps最大值顯示化合物的旋光碳鏈為偶數時具有較大的自發極化值。而傾斜角其結果顯示和旋光碳鏈數沒有明顯的關係。在光電性質的量測上,化合物 I(m=10, n=3), II(m=10, n=4), III(m=10, n=5), IV(m=10, n=3), V(m=10, n=4) and VI(m=10, n=5)在特定的頻率及溫度下具有無閥的光電V型轉換行為。
當旋光中心的側邊取代用氯化甲烷基取代甲烷基可觀察到SmA* 和 SmC* 液晶相的溫度範圍降低,也抑制了SmX*液晶相的生成。且具有較低的澄清點溫度和較高的熔點。其自發極化值和傾斜角,由結果可知旋光中心側邊取代基由甲烷基變成氯化甲烷基時,由於氯化甲烷基具有較大的體積和電負度,因此會產生較大的自發極化值及傾斜角。(Size: H=1.25��, Cl=1.75��; Electronegativity: H=2.1, Cl=3.0)
當硬核結構的組成為PhPhCOOPh時具有較寬廣的液晶相,且SmC*液晶相有較佳的熱穩定性。而當硬核結構由PhPhCOOPh改變為PhCOOPhPh時在相同溫度下會產生較大的自發極化值,但傾斜角的大小沒有顯著的關聯性。
There are many factors affect the properties of ferroelectric chiral Smectic C phase such as chiral group, core structure, linking group, terminal chain length and optical purity. The purpose of this research is looking for a better understanding the relationship between molecular structures and mesomorphic properties.
Thus, new chiral precursor, (S)-1-alkyloxy-3-chloro-2-propanols containing chlomethyl chiral group were designed and synthesized by the reaction of (S)-epichlorohydrin with alcohols under the acid condition. Consequently, six homologous series of chiral compounds, (R)-1-alkyloxy-3-chloro-2-propyl 4-{4’-[(4’’-alkyloxyphenyl)phenylcarbonyloxy]}benzoates, I(m=8-12, n=3), II(m=8-12, n=4) and III(m=8-12, n=5), and (R)-1-alkyloxy-3-chloro-2-propyl 4”-[(4’-alkyloxy)benzoyloxy]biphenyl-4-carboxylate, IV(m=8-12, n=3), V(m=8-12, n=4) and VI(m=8-12, n=5), were synthesized and the mesophases and their corresponding electo-optical properties were investigated. The effect of changing chiral groups from methyl to chloromethyl groups at asymetric carbon, aliphatic alkyl chain length (m), chiral chain length (n), and core structure of the chiral compounds on the mesomorphic and electro-optical properties were compared and discussed.
The results show that, with the exception of compounds IV(m=8, n=3) and VI(m=8, n=5) which possessed exclusively SmA* phase, the rest of compounds displayed SmA* and SmC* phases. The maximum magnitudes of the spontaneous polarization for the chiral compounds, I(m=8-12, n=3), II(m=8-12, n=4), III(m=8-12, n=5), IV(m=9-12, n=3), V(m=8-12, n=4) and VI(m=9-12, n=5), show that compound with even number (n=4) of chiral alkyl chain length has the lager Ps values than that with odd numbers (n=3, 5), but the optical tilt angles have no significant correlation change with chiral chain length. The electro-optical responses of chiral compounds in SmC* phase displayed typical ferroelectric switching behavior. Compounds of I(m=10, n=3), II(m=10, n=4), III(m=10, n=5), IV(m=10, n=3), V(m=10, n=4) and VI(m=10, n=5) in the SmC* phase displayed V-shaped switching property at appropriate frequency and temperature.
The comparison of structurally similar chiral compounds between compounds with chloromethyl substituent and that with methyl substituent at the asymetric carbon of the chiral groups, show that the formers have narrower temperature range of mesophase as well as SmC* phase, higher melting point and lower clearing point than the later ones. In addition, the SmX* phase was surpressed. The elctro-optical measurements show that the maximun Ps values and optical tilt angles are larger for compounds with chloromethyl group than that with methyl group. This may be presumarily due to the lager size and/or electronegativity of the chlorine atom than hydrogen atom (Size: H=1.25��, Cl=1.75��; Electronegativity: H=2.1, Cl=3.0).
The comparison of chiral compounds with difference core structures shows that compounds with PhPhCOOPh core structure have better thermal stability in the the mesophase and ferroelectric SmC* phase than that with PhCOOPhPh core structure. In contrast, the results of the maximun Ps values indicate that compounds with PhCOOPhPh core structure have larger Ps values at the temperature below Curie point than that with PhPhCOOPh core structure. The apparent tilt angles revealed no significant correlation between these two core structures of the chiral compounds.
TABLE OF CONTENTS

ACKNOWLEDGEMENTS V
ABSTRACT VI
中文摘要 VIII
TABLE OF CONTENTS X
LIST OF SCHEME XIII
LIST OF TABLES XIV
LIST OF FIGURES XV
CHAPTER 1 1
INTRODUCTION 1
1.3. Overview 1
1.2. Chiral smectic phases 1
1.2.1 Chiral smectic A phases (SmA*) 1
1.2.2. Chiral smectic C phase (Ferroelectric phase, SmC*) 3
1.3. Motivation of study 10
CHAPTER 2 14
EXPERIMENTAL 14
2.1. Preparation of materials 14
2.1.1. Synthesis of 4-(4’-alkyloxyphenyl)benzoic acids, I-1(m=8-12) 16
2.1.2. Synthesis of 4-[(methyloxycarbonyl)oxy]benzoic acid, I-2 16
2.1.3. Synthesis of 4’-methyloxycarbonyloxybiphenyl-4-carboxylic acid, IV-2 17
2.1.4. Synthesis of (S)-1-propyloxy-3-chloro-2-propanol, I-3 17
2.1.5. Synthesis of (S)-1-butyloxy-3-chloro-2-propanol, II-3 and (S)-1-pentyloxy-3
-chloro-2-propanol, III-3 18
2.1.6. Synthesis of (R)-2-chloro-1-(propoxymethyl)ethyl 4-[(methoxycarbonyl)oxy]
benzoate, I-4 18
2.1.7. Synthesis of (R)-2-chloro-1-(butyloxymethyl)ethyl
4-[(methyloxycarbonyl)oxy]benzoate, II-4, (R)-2-chloro-1-(pentyloxymethyl)ethyl 4-[(methyloxycarbonyl)oxy]benzoate, III-4, (R)-2-chloro-1-(propyloxymethyl)ethyl 4’-methyloxycarbonyloxybiphenyl-4-carboxylate, IV-4, (R)-2-chloro-1-(butyloxymethyl)ethyl 4’-methyloxycarbonyloxybiphenyl-4-carboxylate, V-4 and (R)-2-chloro-1-(pentyloxymethyl)ethyl 4’-methyloxycarbonyloxybiphenyl-4-carboxylate, VI-4 19
2.1.8. Synthesis of (R)-2-chloro-1-(propyloxymethyl)ethyl 4-hydroxybenzoate, I-5 20
2.1.9. Synthesis of (R)-2-chloro-1-(butyloxymethyl)ethyl 4-hydroxybenzoate, II-5, (R)-2-chloro-1-(pentyloxymethyl)ethyl 4-hydroxybenzoate, III-5, (R)-2-chloro-1-(propyloxymethyl)ethyl 4-(4’-hydroxyphenyl)benzoate, IV-5, (R)-2-chloro-1-(butyloxymethyl)ethyl 4-(4’-hydroxyphenyl)benzoate, V-5 and (R)-2-chloro-1-(pentyloxymethyl)ethyl 4-(4’-hydroxyphenyl)benzoate, VI-5 20
2.1.10. Synthesis of (R)-1-propyloxy-3-chloro-2-propyl 4-{4’-[(4’’-alkyloxyphenyl)
phenylcarbonyloxy]}benzoates, I(m=8-12, n=3) 21
2.1.11. Synthesis of (R)-1-butyloxy-3-chloro-2-propyl 4-{4’-[(4’’-alkyloxyphenyl)
phenylcarbonyloxy]}benzoates, II(m=8-12, n=4) 22
2.1.12. Synthesis of (R)-1-pentyloxy-3-chloro-2-propyl 4-{4’-[(4’’-alkyloxyphenyl)
phenylcarbonyloxy]}benzoates, III(m=8-12, n=5) 22
2.1.13. Synthesis of (R)-1-propyloxy-3-chloro-2-propyl 4”-[(4’-alkyloxy)benzoyloxy]
biphenyl-4-carboxylate, IV(m=8-12, n=3) 23
2.1.14. Synthesis of (R)-1-butyloxy-3-chloro-2-propyl 4”-[(4’-alkyloxy)benzoyloxy]
biphenyl-4-carboxylate, V(m=8-12, n=4) 24
2.1.15. Synthesis of (R)-1-pentyloxy-3-chloro-2-propyl 4”-[(4’-alkyloxy)benzoyloxy]
biphenyl-4-carboxylate, VI(m=8-12, n=5) 24
2.2. Physical properties 26
2.2.1. Chemical Structure Identificatio 26
2.2.2. Masophase Identification 26
2.2.3. Preparation of homogenous cells 27
2.2.4. Alignment of liquid crystals in SSFLC Cells 27
2.2.5. Switching behavior measurement 28
2.2.6. The spontaneous polarization (Ps) measurement 28
2.2.7. Optical tilt angle measuremen 31
2.2.8. The optical response measurement 32
CHAPTER 3 33
RESULTS AND DISSCUSSION 33
3.1. Chemical structure identification 33
3.1.1. Mesophase studies 33
3.2. The effect of achiral and chiral chain length on the mesomorphic properties of series I(m=8-12, n=3), II(m=8-12, n=4) and III(m=8-12, n=5) 34
3.2.1. Optical microscopy observations and phase transition behavior of series I(m=8-12, n=3), II(m=8-12, n=4) and III(m=8-12, n=5) 34
3.2.2. Switching current behavior 40
3.2.3. Switching current behavior 42
3.2.4. Optical tilt angle (θ) 44
3.2.5. Electric-optical response 46
3.3. The effect of achiral and chiral chain length on the mesomorphic properties of series IV(m=8-12, n=3), V(m=8-12, n=4) and VI(m=8-12, n=5) 47
3.3.1. Optical microscopy observations and phase transition behavior of series IV(m=8-12, n=3), V(m=8-12, n=4) and VI(m=8-12, n=5) 47
3.3.2. Switching current behavior 53
3.3.3. Spontaneous polarization (Ps) 55
3.3.4. Optical tilt angle (θ) 57
3.3.5. Electric-optical response 59
3.4. The effect of lateral substituent changing to chloromethyl in the chiral center on the mesophases and electro-optical properties 60
3.4.1. Transition temperatures and mesophases behavior of series I and PPmPPB 60
3.4.2 The comparison of Spontaneous polarization (Ps) between I(m=8-12, n=3) and PPmPPB 64
3.4.3. The comparison of Optical tilt angle (θ) between I(m=8-12, n=3) and PPmPPB 66
3.5. The effect of various core structures on the mesophases and electro-optical properties 68
3.5.1. Transition temperatures and mesophases behavior 68
3.5.2 Spontaneous polarization (Ps) 72
3.5.3. Optical tilt angle (θ) 74
CHAPTER 4 76
CONCLUSIONS 76
REFERENCES 78
APPENDIX 80
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