Relationship between the ability to control liquid crystal alignment and wetting properties of calix[4]resorcinarene monolayers
Relationship between the ability to control liquid crystal alignment and wetting properties of calix[4]resorcinarene monolayers
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DOI：
10.1039/b007739i
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发表时间：
2001
影响因子：
--
通讯作者：
Sang-keun Oh;M. Nakagawa;K. Ichimura
中科院分区：
文献类型：
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作者：
Sang-keun Oh;M. Nakagawa;K. Ichimura
本文描述了两个o -八羧基甲基化杯状[4]间苯二甲酸（CRA-CMs）与全氟辛基或辛基偶氮苯共吸附形成的混合单层的向列相液晶（LC）排列控制能力与润湿性能之间的关系。CRA-CM单层膜的光照射引起表面偶氮苯的可逆光异构化反应，导致单层膜的LC取向和润湿性发生变化。光生成的LC排列受混合单层的表面组成的显著影响。用对辛基偶苯修饰的单组分CRA-CM单层基板制成的LC细胞，在非偏振紫外光的斜照射下，LC分子的取向由同向异性变为向光传播方向倾斜的均匀排列。相比之下，含有对全氟辛基苯的单组分和混合单层CRA-CM分别引起各向同性排列和高预倾斜角度的倾斜排列。CRA-CM单层的光异构化水平和表面自由能不是引起取向行为差异的充分条件。我们的结论是，分子水平的形貌和/或流动度，由表面各向异性液体的接触角滞后推断，是诱导所观察到的LC排列变化的最重要因素。
This paper describes the correlation between the ability to control nematic liquid crystal (LC) alignment and wetting properties of mixed monolayers formed by coadsorption of two O-octacarboxymethylated calix[4]resorcinarenes (CRA-CMs) with either perfluorooctyl- or octylazobenzene units. Photoirradiation of CRA-CM monolayers induces reversible photoisomerization reaction of the surface azobenzenes, which causes changes in LC alignment and wettability of the monolayers. The photogenerated LC alignments are considerably influenced by the surface compositions of the mixed monolayers. When LC cells fabricated with substrate plates modified with single-component monolayers of CRA-CM with p-octylazobenzenes are subjected to oblique irradiation with non-polarized UV light, the orientation of LC molecules is changed from homeotropic to homogeneous alignments tilting toward the direction of light propagation. In contrast, single-component and mixed monolayers of CRA-CM with p-perfluorooctylazobenzenes cause homeotropic alignments and tilted alignments with high pretilt angles, respectively. The level of photoisomerization and surface free energy of the CRA-CM monolayers are not a sufficient condition to cause the contrasting alignment behaviors. We conclude that the molecular-level morphology and/or fluidity of the monolayer surfaces of CRA-CMs, which is deduced from the contact angle hysteresis of anisotropic liquids for the surfaces, is the most significant factor to induce the LC alignment alterations observed.