侧基膨胀效应和偶合作用对液晶高分子相重入行为调控的研究

Liquid-crystalline polymers (LCPs) have attracted much interest because of their potential applications. Moreover, the realization of these applications strongly depends on the condensed state structure of LCPs. In this project, a series of LCPs with the expansible bulky side groups will be designed and synthesized based on the idea of the mechanism of the re-entrant isotropic phase of mesogen-jacketed LCPs and the molecular structure of side-chain LCPs. The molecular structure characteristic of bulky side groups is that the several alkyl tails are introduced into the outside of rigid core, containing the benzene ring, disc-shaped triphenylene and rod-shaped hemiphasmidic mesogen. The phase behavior and the phase structure of the polymers will be investigated. The strong and weak of the “side-group expansion effect” and “coupling effect” can be controlled by changing the volume of expansible side group, the length of spacer and the kind of main chain in order to research the strong and weak of “dynamic steric effect”. Therefore, it will reveal the essence of re-entrant isotropic phase of LCPs. On the other hand, it will tailor the re-entrant isotropic phase and the chain conformation of LCPs. This work will provide new ideas and methods for manipulating the condensed state structure of LCPs.

液晶高分子受到人们的广泛关注与它的潜在应用前景是分不开的。然而，这些应用前景的实现与液晶高分子的凝聚态结构调控密切相关。本项目申请人从甲壳型液晶高分子的相重入行为形成机理和侧链型液晶高分子的分子结构模型出发，拟设计和合成多系列含有可膨胀的庞大侧基的液晶高分子，其中可膨胀的庞大侧基的分子结构特点是在苯环，盘状苯并菲核或棒状hemiphasmidic液晶刚性核外引入多条烷烃尾链。通过研究可膨胀的庞大侧基体积大小，间隔基长度和主链类型对液晶高分子相行为和相结构的影响，探讨“侧基膨胀效应”和“偶合作用”的强弱对动态“空间效应”强弱的影响，从而揭示液晶高分子相重入行为的本质，达到调控液晶高分子的相重入行为和高分子链的刚柔性的目的。通过本课题的研究工作，为调控高分子的凝聚态结构提供新的思路和方法。

液晶高分子材料的实际应用与液晶高分子的凝聚态结构密切相关。然而，探索液晶相的形成机理，进而调控液晶高分子的相行为和相结构是制备高性能的液晶高分子材料的关键。本项目通过系统研究侧基体积大小，间隔基长度，烷烃尾链长度，主链类型对含有可膨胀的庞大侧基的液晶高分子相行为和相结构的影响，探讨出“侧基膨胀效应”和“偶合作用”的强弱对动态“空间效应”强弱的影响，揭示出液晶高分子液晶相形成机理和相重入行为的本质，最终达到对液晶高分子的相形为和相结构调控的目的。本项目主要取得了如下成果：（1）合成一系列不可定向排列的可膨胀的庞大侧基的液晶高分子：甲壳型液晶高分子和树枝状侧基液晶高分子。研究发现，该类液晶高分子的相重入行为依赖于间隔基长度，刚性核大小以及烷烃尾链长度，数目和代数。（2）合成一系列可定向排列的可膨胀的庞大侧基的侧链型液晶高分子：苯并菲侧链型液晶高分子和Hemiphasmidic侧链型液晶高分子。通过改变主链类型，间隔基长度和尾链长度，该类液晶高分子形成柱状相或者近晶相，不能形成各向同性重入相。通过本课题的研究工作，为开发高性能的液晶高分子材料提供新的思路和方法。已发表标注有本项目编号的论文10篇，包括Polymer Chemistry 2篇，Physical Chemistry Chemical Physics 1篇，New Journal of Chemistry 1篇，Liquid Crystals 1篇，Journal of Polymer Science Part A: Polymer Chemistry 1篇等。