REVERSIBLE ALIGNMENT CHANGE OF LIQUID-CRYSTALS INDUCED BY PHOTOCHROMIC MOLECULAR FILMS .13. FACTORS AFFECTING PHOTOINDUCED ALIGNMENT REGULATION OF CYCLOHEXANECARBOXYLATE-TYPE NEMATIC LIQUID-CRYSTALS BY AZOBENZENE MOLECULAR FILMS
REVERSIBLE ALIGNMENT CHANGE OF LIQUID-CRYSTALS INDUCED BY PHOTOCHROMIC MOLECULAR FILMS .13. FACTORS AFFECTING PHOTOINDUCED ALIGNMENT REGULATION OF CYCLOHEXANECARBOXYLATE-TYPE NEMATIC LIQUID-CRYSTALS BY AZOBENZENE MOLECULAR FILMS
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DOI：
10.1021/la00039a044
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发表时间：
1992-03-01
期刊：
影响因子：
3.9
通讯作者：
ICHIMURA, K
中科院分区：
文献类型：
--
作者：
AOKI, K;SEKI, T;ICHIMURA, K
偶氮苯单元通过Si-O键连接在石英板上，当将向列相液晶（LC）置于覆盖有偶氮修饰表面（称为“命令面”）的两个板之间时，可以实现可逆的光异构化，并调节向列相液晶（LC）在各向同性和平面模式之间的排列。偶氮苯单元的分子结构和占用面积对指令面的效率有重要影响。在分子结构效应方面，偶氮苯部分取代基的疏水性在分子的排列调节中起着重要作用。硅基化的方式和偶氮苯段与硅基之间间隔单元的长度也是控制取向调节的关键因素。有一个关键的区域，由偶氮苯单元占用的光调节的LC对准。大于约120埃的占位面积导致没有光调节。被占领的区域也影响光响应模式，并讨论了光调节的命令表面属性阈值的存在。研究了光电池厚度和曝光周期对光响应的影响。
Azobenzene units attached on quartz plates through Si-O bonding exhibit reversible photoisomerization and regulate the alignment of a nematic liquid crystal (LC) between homeotropic and planar modes when LC cells are constructed by putting the LC between two plates covered with the azo-modified surfaces which have been called "command surfaces". The efficiency of the command surfaces is affected crucially by the molecular structure and the occupied area of azobenzene unit. Concerning the molecular structural effect, the hydrophobic nature of a substituent at the azobenzene moiety holds an important role in the alignment regulation. The mode of silylation and the length of a spacer unit between the azobenzene moiety and the silylating group are key factors in commanding the alignment regulation as well. There is a critical area occupied by an azobenzene unit for the photoregulation of LC alignment. An occupied area larger than ca. 120 angstrom2 results in no photoregulation. The occupied area also affects the photoresponse pattern, and discussion is given on the existence of a threshold of the command surface property for the photoregulation. Effects of cell thickness and the exposure cycles on the photoresponse are also presented.