多重掌性中心對膽固醇液晶相生成的探討：主鏈結構為2,3-雙氧丙烯基-L-蘇來醇的共聚高分子與寡聚物

Abstract

近年來由於液晶工業的發達，因應各種需求的液晶材料也陸續被開發出來，其中，膽固醇液晶（cholesteric LC）因具有雙穩定性（bistability），可以於不外加電壓下仍能保持畫面的表現，有機會成為新一代的平面顯示技術。膽固醇液晶的材料特性，源於其同時兼具了掌性螺旋結構與液晶性質。螺旋結構的產生，通常是將摻雜掌性分子（chiral dopant）於不帶掌性的液晶分子中而產生的。因此，掌性分子的螺旋扭轉力（helical twisting power, HTP）是決定液晶螺旋扭轉程度的主要因素。在化學的觀點裡，液晶分子的螺旋扭轉是因為掌性分子進入所引起的，也可以說是液晶以巨觀螺旋排列的形式來”表達”微小的分子掌性。因此，液晶分子如何表達摻雜分子的掌性一直是很有趣的題目。一般來說，每種掌性結構有其不同的HTP，而當許多掌性結構被組合於同一分子鏈上時，往往無法於液晶中表現規律的分子構形，而使得HTP變得無法預測。本論文藉由有機合成設計，合成了一系列具有相同掌性中心與液晶原基團（mesogenic group）但不同重複單元數的有機化合物（主鏈結構為2,3-雙氧丙烯基-L-蘇來醇的共聚高分子與寡聚物，如下圖）。藉由液晶原基團的改變，我們成功地使摻雜分子於液晶中表現出規律的構形，使其HTP對掌性結構數呈現加成性。並確認了即使分子量達到6100，其規律性質仍能與小分子一致。

When chiral compounds were dissolved in nematic liquid crystals, cholesteric phases may be induced. It is a very fascinating about their ability to transfer and magnify the chiral information from dopant molecules into liquid crystals. The property of cholesteric phase is directly dependent on the dopant which means the induced cholesterics may be tunable if a dopant sensitive to photo or electric field stimulation was doped. The most important property of chiral dopants is the helical twisting power(HTP, βM), which is a measurable parameter of their ability to produce twisted phase. Investigations of the correlation between molecular structure and phase chirality have been successful in some system, but there is no exact study in a family of compounds with systematic variation of the number of effective chiral inducers. The series of regioregular oligo(phenylenevinylene) oligomers and polymer in our system perform additively HTP(Helical twisting Power)s up to the molecular weight of 6100. In addition, the chiral induction ability increases with the molecular weight. This study provide a new strategy to design molecules with regular HTPs.