含矽氧連結基及旋光軟鏈段之氫鍵香蕉型液晶三元體與主鏈型高分子之研究

Abstract

本文實驗合成出含二或三個矽氧連結基在中心和不同芳香環在兩側末端之五種雙頭酸，並與有無加入旋光中心之單□啶、雙□啶混合，混摻出多種三元體與主鏈型高分子之氫鍵香蕉型液晶。利用H1-NMR、EA作為結構鑑定後，以POM、DSC、XRD及電性量測探討其液晶行為。 結果顯示兩個矽氧連結基之分子在硬段較短的情況下會失去液晶相，但在同樣硬段下三個矽氧連結基分子則會有液晶相；此外，變換芳香環種類使液晶基更剛硬，有利增廣液晶相範圍。在加入旋光中心後，可使無液晶相分子轉成有液晶相，也可使原本較高之液晶溫度略微下降，並提升液晶相溫寬。由於氫鍵分子設計關係，我們能獲得的相均為層列相C (SmC)。

In this study, five types of diacids containing two or three siloxane linking groups in center and various aromatic rings at both terminals were synthesized. These diacids were mixed with pyridine and bipyridine, with or without chiral center, to form H-bonded banana-shaped triads and main-chain polymers. The chemical structures were characterized by H1-NMR and EA, and the liquid crystalline(LC) phases and mesomorphic behavior of all these compounds were investigated using POM, DSC, XRD, and Electro-optical measurement.. It was found that two siloxane linking groups with short mesogenic group could lose its LC phase, while three siloxane linking groups with the same mesogenic group could obtain LC phase. Furthermore, increasing the rigidity of aromatic rings could increase LC range. Adding the chiral center, allows non-LC phase products to turn into LC phase, slightly decreases the LC temperature, and broadens the LC temperature range. Due to the H-bonded molecular design, all the phases we obtained are smectic C (SmC).