Synthesis and Property of Unsymmetric Bent-core Liquid Crystals Based on 2,5-Disubstitueted-1,3,4-oxadiazole

Abstract

Two novel series of bent-core liquid crystals (9a～9e and 10a～10e) were prepared with a central bent core based on 2,5-disubstitueted-1,3,4-oxadiazole, ester group bridge (coo), alkyl tails with different carbon numbers (n＝5～9), and one side wing substituted by fluorine atom. The structures of the target compounds were confirmed by IR, 1 H NMR, 13 C NMR, MS, and their transition temperatures and phase textures were investigated by using differential scanning calorimetric (DSC) and polarizing optical microscopy (POM). The result suggested that all target compounds had right chemical structure. All compounds 9a～9e and 10a～10e exhibited nematic phase and existed wide temperature range of nematic phase. The widest range of nematic phase was 78 ℃. The temperature range of nematic phase of compounds 9a～9e with lateral monofluoro-substituted benzene was more narrow than compounds 10a～10e with lateral difluoro-substituted benzene. Moreover, compounds 9a～9e showed odd-even effect.

Synthesis and Properties of Thiadiazole Bent-Core Liquid Crystal with Difluorooxymethylene-Bridge

“…近年来人们通过改变中心基团、 桥键、 末端链以及苯环侧位引入取代基的方式, 以求获得低熔 点、宽向列相弯曲形液晶材料 [7,8] . 2011 年, Jens 等 [14] 合成了以噁二唑为中心环, 酯基为桥键的不对称弯曲形 化合物, 其向列相范围最大可达到 75 ℃, 但部分化合 物呈现复杂的近晶相, 也不利于研究使用. 由此可见, 相对于亚甲氧基和酯基, 二氟亚甲氧基为桥键对液晶化 合物有很大的改进, 不仅如此二氟亚甲氧基的引入可降 低液晶化合物的粘度,减少对温度的依赖性 [15] .…”