有机环四硅氧烷液晶的合成及其相变行为

Synthesis and Phase Behavior of 1-Mesogenic Group1,3,3,5,5,7,7-Heptamethyl-Cyclotetrasiloxanes

两种环四硅氧烷分别和６种液晶基元化合物（Ｍ１－６）反应，合成了６种仅含１个介晶侧基的环四硅氧烷（１－６）。它们的化学结构已由１ＨＮＭＲ、ＩＲ和元素分析证实。借助ＤＳＣ和偏光显微镜观察研究了１２个（Ｍ１－６和１－６）化合物的相变行为。结果表明８个化合物（Ｍ３－６和３－６）均呈现液晶相变。实验结果证明在这类液晶化合物中存在环状结构的硅氧烷不仅扩大了液晶态的温度范围，而且还有利于液晶分子的取向。

Six new cyclotetrasiloxanes(1- 6) with only one mesogenic group in the molecule were obtained by reacting two organocyclotetrasiloxanes with six mesogenic compounds (M1 -M6) respectively. Their chemical structures were confirmed by IR, 1H NMR and elemen tal analysis. Their phase behavior was also investigated by using differential scanning calorimetry and polarizing microscopy, The results show that eight compounds(M3-M6, 3-6) exhibit liquid crystalline phase transition。 The experimental results also prove that the existence of the siloxane cyclic structure can not only enlarge the temperature range of mesomorphic state in the LC compound, but also be favorable for the LC molecular orientation.