甲壳型液晶-南开大学讲座稿 2007

Liquid Crystals几种液晶相的结构示意图

Nematic Smectic A Smectic C

Nematic Columnar

Ingo Dierking, Textures of Liquid Crystals, Wiley-VCH, Verlag, 2003

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ON 液晶在显示器中的工作原理

Principle of twisted nematic (TN) LCD

in the normally white mode

Liquid Crystalline Polymers 液晶高分子Main-Chain Type LCP 主链型

Main -

Chain Type LCP

Side -Chain Type LCP 侧链型

Liquid Crystalline Polymers

侧链型液晶高分子液晶相的生成能力及液晶相稳定性•取决于聚合物的三个主要组成部分:主链、液晶基元以及两者间的连接成分

－分子主链－－→无规线团构象

－液晶基元－－→取向有序的液晶态

•两种可能：

-侧链的运动屈服于主链的运动－－→各向同性相-主链运动屈服于侧链运动－－→液晶性

主链和侧链相互竞争使液晶性能否出现难以预料。•“柔性间隔段去偶合”----Finkelmann

在主链和侧链的液晶基元之间插入足够长的柔性间隔基，以减弱主链对侧基的干扰，从而保证液晶基元有序排列不受影响。

Main -

Chain Type LCP

Side -Chain Type LCP 侧链型

Liquid Crystalline Polymers

去偶合理论前提：

侧基（液晶基元）有序排列，

主链运动破坏侧基有序

反思：

侧基（液晶基元）有序排列→分子有序；

主链运动破坏侧基有序→侧基帮助主链取向有序

对策: 甲壳型液晶高分子MJLCP：

液晶基元重心连接/ 免除柔性间隔

侧基（体积、刚性、稠密度）强迫主链取向

Banded Texture of a Mesogen-Jacketed LCP at 210o C

1. Introduction
Comparison of the three LCPs (Why study MJLCPs ?) MCLCP
主链型
SCLCP
侧链型
MJLCP
甲壳型
Polymerization LC ordering Property Applcation
Condensn. Molecular Semi-rigid HSHM
Addition Molecular Flexible Opt-electr.
Addition (Supra)molecular Semi-rigid ?

US Air Force LC MURI Project (1999)
Manipulation of molecular arrangement and function through synthesis and processing Understanding the formation and role of defects on LC properties Controlling LC behavior through the application of applied internal and external fields Exploiting new opportunities The Mesogen-Jacketed Liquid Crystalline Polymer （甲壳 型液晶高分子）was proposed as new opportunity for next generation LCPs Caltech Colorado Cornell Kent MIT Northwestern Arizona USC Amoco Displaytech Hughes

Why Mesogen-Jacketed LC Polymers ?
(by Ober C. K., Mather P. T., Thomas E. L. & Kornfield J. A.)
• Novel “main chain” LC polymers made by living radical polymerization • Model materials with controlled architectures • Fibers and melt processing possible • Unusual molecular structure and melt history effects • New concepts in LC polymers

去偶合理论前提： 侧基（液晶基元）有序排列， 主链运动破坏侧基有序 反思： 分子有序； 侧基帮助主链取向有序 解决方案: MJLCP： 液晶基元重心连接 / 免除柔性间隔 侧基（体积、刚性、稠密度）强迫主链取向
再反思： 刚性棒状液晶基元？ 柔性的？弯曲的？树枝状的？

• MJLCPs ---- new design strategy for LCPs
Mol. Cryst. Liq. Cryst. 1993, 231, 107
Macromolecules 1999, 32, 4494
Macromol. Rapid Commun. 1999, 20, 555
“A new strategy for the design of liquid crystalline polymers with flexible and apolar building blocks”
Chin. J. Polym. Sci. 2003, 21, 21
n = 4 - 8, 12;