新型(S)-2-(6-甲氧基-2-萘基)丙酸衍生之旋光性液晶材料的合成與性質的研究

SYNTHESIS AND PROPERTIES OF NOVEL CHIRAL LIQUID CRYSTALS DERIVED FROM (S)-2-(6-METHOXY-2-NAPHTHYL)PROPIONIC ACID

林子欽(Tzu-Chin Lin)

指導教授 ： 吳勛隆

大同大學/工程學院/化學工程學系所/碩士(2004年)

摘要

本研究目的是探討旋光性末端烷鏈部份對於液晶相及其物性的影響。以(S)-2-(6-methoxy-2-naphthyl)propionic acid為起始物合成出七個具有不同旋光性尾鏈結構以探討化合物不同結構的旋光烷鏈與液晶相的關係。
第一部分合成兩系列旋光性燕尾型液晶材料:(S)-2-(6-(4-(4¢-alkanoyloxyphenyl
))benzoyloxy)-2-napthyl)propionate, PmPBNP (m=7-11) 和2-ethyl-1-butyl
(S)-2-(6-(4-(4¢-alkanoyloxyphenyl)benzoyloxy)2-napthyl)propionate, EBmPBNP
(m=7-11)，探討以燕尾結構作為旋光尾鏈對於液晶相及其物性的影響。
化合物PmPBNP (m=7-8)具有Iso-N*-TGBA*-SmA*-CrX*-Cr的相順序而化合物PmPBNP (m=9-11)具有Iso-N*-TGBA*-SmA*-SmCA*-CrX*-Cr的相順序。隨著增加非旋光烷鏈的長度會增加SmCA*相的熱穩定性但是SmA*的溫度範圍卻會變小。電流轉換行為、可溶混性實驗和介電性質的研究證實這系列的液晶材料具有反誘電性液晶相(SmCA*)的存在，在自發極化值方面隨著非旋光烷鏈的增加而自發極化值也隨之增加。在反誘電液晶相中可以得到無閥值之V型轉換行為。
化合物EBmPBNP (m=8-11)具有Iso-N*-SmA*-SmC*-CrX*-Cr的相順序而EB7PBNP則具有Iso-N*-SmA*-CrX*-Cr的相順序。當增加非旋光烷鏈的長度SmC*相的溫度範圍變廣而SmA*相的溫度範圍變窄。在燕尾結構與旋光中心間增加一個甲基會降低液晶相的熱穩定性。在自發極化值方面隨著非旋光烷鏈的增加而自發極化值也隨之增加；而在光電應答的研究顯示這系列的化合物在誘電性液晶相中可以得到無閥值之V型轉換行為。
第二部分合成四系列含有氟化烷鏈之液晶材料PBNP(p,m,n) (p=7-11; m=3, n=2; m=2, n=4; m=3, n=4; m=2, n=6)，探討以半氟化烷鏈作為旋光尾鏈對於液晶相及其物性的影響。此外合成一個不含半氟化烷鏈之液晶材料PBNP(p,6,0) (p=7-11)與PBNP(p,2,4) (p=7-11)比較。
化合物PBNP(p,m,n) (p=7-11; m=3, n=2; m=2, n=4; m=3, n=4; m=2, n=6)大多都具有Iso-SmA*-SmC*-Cr的相順序，實驗結果顯示導入半氟化烷鏈於旋光尾鏈的確能有利於層列相(smectic phases)的產生並且會增加液晶相的熱穩定性。由化合物的紋理圖鑑定、電流轉換行為、自發極化值和介電性質研究顯示這些旋光性液晶材料確實具有SmC*相的存在。光電應答的結果顯示在SmC*相中具有無閥值之V型轉換行為。此外無論含有半氟化烷鏈的PBNP(p,2,4)系列和不含半氟化烷鏈的PBNP(p,6,0)系列在SmC*相中都具有無閥值之V型轉換行為。
綜合以上結果得知以(S)-2-(6-methoxy-2-naphthyl)propionic acid為起始物合成出的旋光性液晶材料似乎有利於產生無閥值之V型轉換行為，這些結果可以作為日後液晶分子設計的重要參考。

關鍵字

誘電性液晶 ； 液晶

並列摘要

The aim of the research work was intended to study the effect of terminal chiral chain moiety on the mesophases and mesomorphic properties. By means of chiral compound, (S)-2-(6-methoxy-2-naphthyl)propionic acid as building block, seven homologous series of liquid crystal materials comprised of different chiral chain were synthesized for investigating the correlation between the chemical structure of chiral tails and mesomorphic properties.
Chiral swallow-tailed compounds (S)-2-(6-(4-(4¢-alkanoyloxyphenyl))benzoyl-
oxy)-2-napthyl)propionate, PmPBNP (m=7-11) and 2-ethyl-1-butyl (S)-2-(6-(4-(4¢-
alkanoyloxyphenyl)benzoyloxy)2-napthyl)propionate, EBmPBNP (m=7-11) were synthesized for studying the effect of swallow-tailed moiety of chiral chain on mesomorphic properties.
Compounds PmPBNP (m=7-8), display enantiotropic mesophases of the N*, TGBA*, SmA* and CrX* phases whereas the materials PmPBNP (m=9-11) show enantiotropic mesophases of the N*, TGBA*, SmA* and SmCA* phases. An increasing chain length of methylene (m) can enhance the thermal stability of the SmCA* phase, but the temperature range of the SmA* phase decreases. The study of switching curve, miscibility study and dielectric property demonstrates that the series of chiral materials possess SmCA* phase. The magnitude of spontaneous polarization for materials PmPBNP(m=9-11) increase as the length of achiral aliphatic chain increases. The thresholdless, V-shaped switching property can be obtained in the SmCA* phase.
Compounds EBmPBNP (m=8-11) show the enantiotropic mesophases of the N*, SmA*, SmC* and CrX* phases whereas compound EB7PBNP shows enantiotropic mesophases of the N*, SmA*, and CrX* phases. As the chain length of terminal achiral chains increasing, the temperature range of the SmC* phase becomes wide while that of the SmA* phase becomes narrow. Moreover, extending of a methylene between chiral center and swallow-tailed moieties leads to suppress the thermal stability of mesophases. The magnitude of spontaneous polarization for materials EBmPBNP (m=8-11) increase as the length of achiral aliphatic chain increases. The study of electro-optical response indicates that this series of chiral materials in the SmC* phase exhibit thresholdless, V-shaped switching property.
Four homologous series of chiral semi-fluorinated liquid crystals, PBNP(p,m,n) (p=7-11; m=3, n=2; m=2, n=4; m=3, n=4; m=2, n=6), were synthesized for investigating the influence of semi-fluorinated chain on mesomorphic properties. In addition, a homologous series of non-fluorinated compounds, PBNP(p,6,0), were synthesized in order to compare to the fluorinated compounds, PBNP(p,2,4).
Compounds PBNP(p,m,n) (p=7-11; m=3, n=2; m=2, n=4; m=3, n=4; m=2, n=6) mostly show the enantiotropic mesophases of SmA* and SmC* phases. The results reveal that introduction of semi-fluorinated chain on chiral tails indeed favor the formation of the smectic phases and enhance the thermal stability of the mesophases. The study of texture observation, switching current behavior and dielectric properties demonstrates that these chiral materials truly possess existence of the SmC* phase. The results of the electro-optical response exhibit the thresholdless, V-shaped switching property in the SmC* phase. Furthermore, both non-fluorinated and fluorinated compounds, for example of PBNP(p,6,0) and PBNP(p,2,4), the V-shaped switching can be obtained in the SmC* phase at appropriate frequency and temperature.
In conclusion, the results indicate that these chiral materials derived from (S)-2-(6-methoxy-2-naphthyl)propionic acid seem favorable for the formation of the thresholdless and V-shaped switching properties.

並列關鍵字

ferroelectric liquid crystals ； liquid crystals

參考文獻

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