探討分子結構對TGB液晶相穩定度以及旋光性液晶相性質的影響

EFFECT OF MOLECULAR STRUCTURE ON THE STABILTY OF TGB PHASE AND MESOMORPHIC PROPERTIES OF THE CHIRAL LIQUID CRYSTALS

張瑞洋(Jui-Yang Chang)

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

從近來來的文獻顯示，影響TGB液晶相生成的因素有很多，如立體障礙、連結基與燕尾型結構。本研究的目的為進一步的了解分子結構與TGB液晶相生成的關係。
因此，本實驗以(S)-2-(6-methoxy-2-naphthyl)-propionic acid 為起始物合成了四個系列具有methyleneoxy連接基之旋光性化合物與一個系列具有重氫原子連接基之旋光性化合物，藉著改變液晶材料的分子結構上的連接基、非旋光末端烷鏈及旋光烷鏈，並探討分子結構對液晶相及其物性的關係與影響。
實驗結果顯示，大多數所合成出的液晶材料皆具有TGBA*液晶相，S1H-m和S3H-m兩系列的液晶材料皆呈現出寬廣的TGB液晶相溫度範圍。而且，TGBC*和SmC*液晶相的溫度範圍大致上隨著非旋光烷鏈鏈長增加而增加。此外，當重氫原子取代連接基methyleneoxy上的氫原子時，N*液晶相消失且產生一直接由Iso到TGBA*的相轉變。
誘電性層列C*液晶相的自發性極化值的大小是藉由表面穩定理論與在5µm厚度的均勻試片條件下測量。化合物SnX-m自發行極化值的最大值介於15nC/cm2 到41 nC/cm2之間。
總而言之，從結果顯示出連結基的種類、燕尾結構與末端與非旋光烷鏈鏈長的確會對於TGB液晶相的生成與溫度範圍具有很明顯的影響。此研究結果對TGB液晶相的研究上提供了相當多有系統的證據。

關鍵字

液晶 ； 誘電性液晶 ； TGB液晶相

並列摘要

ABSTRACT
From the results of recent paper, there are many factors effect the TGB phase formation such as steric, linking group and swallow tail structure. The purpose of this research is apt for a better understanding the relationship between molecular structure and TGB phase formation.
Four homologous series of chiral materials with methleneoxy linking group, alkyl (S)-2-(6-(4-(4´-alkoxyphenyl)benzyloxy)-2-naphthyl)propionates, SnH-m, and one homologous series of chiral materials with deuterated methleneoxy linking group, d2-3-ethylbutyl (S)-2-(6-(4-(4´-alkoxyphenyl)benzyloxy)-2-naphthyl)propionates, S2D-m , derived from (S)-2-(6-methoxy-2-naphthyl)-propionic acid, were designed, synthesized and investigated on the structure property relationship in the chiral liquid crystals.
The target compounds were independently modified by the linking group, length of terminal chain and chiral chain. Most of the compounds showed TGBA* phase. Both materials of S1H-m and S3H-m exhibited a wide temperature range of TGB phases and the temperature ranges of TGBC* and SmC* phase were mainly increasing with increasing terminal alkyl chain. Furthermore, when deuterium substituted for hydrogen atoms at the methyleneoxy linking group, in S2D-m the N* phase was disappeared and a direct Iso-TGBA* phase transition formed.
The magnitudes of spontaneous polarization of the ferroelectric SmC* phase were measured in a 5µm homogeneously aligned cell by the surface stabilized geometry. The largest Ps values of SnX-m were from 15nC/cm2 to 41 nC/cm2 and have no relation to the terminal alkyl chain.
In a conclusion, the results from above indicate that the linking group, swallow-tail structure and length of alkyl chain indeed have the significant effect on the incidence and stability of TGB phase. The systematic studies provide systematic evidences that the structure effect on the formation of the TGB phase.

並列關鍵字

LIQUID CRYSTALS ； TGB phase

參考文獻

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