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首页> 外文期刊>Journal of Colloid and Interface Science >Influence of 4-cyano-4 '-biphenylcarboxylic acid on the orientational ordering of cyanobiphenyl liquid crystals at chemically functionalized surfaces
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Influence of 4-cyano-4 '-biphenylcarboxylic acid on the orientational ordering of cyanobiphenyl liquid crystals at chemically functionalized surfaces

机译：4-氰基-4'-联苯羧酸对氰基联苯液晶在化学官能化表面上取向顺序的影响

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摘要

We report two methods that involve tailoring of the chemical composition of the nematic liquid crystal 4-cyano-4'-pentylbiphenyl to achieve control over the orientational ordering of the liquid crystal on chemically functionalized surfaces. The first method involves the direct addition of 4-cyano-4'-biphenylcarboxylic acid to 4-cyano-4'-pentylbiphenyl. The second method involves exposure of 4-cyano-4'-pentylbiphenyl to ultraviolet light and photochemical generation of a range of products, including 4-cyano-4'-biphenylcarboxylic acid. The addition of the acid or exposure to ultraviolet light accelerated the rate at which the liquid crystal exhibited an orientational transition from planar to perpendicular (homeotropic) alignment on surfaces presenting ammonium groups. The appearance of the homeotropic orientation of the UV-treated 4-cyano-4'-pentylbiphenyl on ammonium-terminated Surfaces was dependent on the thickness of the film of liquid crystal (13-50 mu m), consistent with a dipolar coupling between the liquid crystal and the electric field associated with an electrical double layer generated at the ammonium surface. Although the addition of 4-cyano-4'-biphenylcarboxylic acid or UV treatment of the liquid crystal also promoted homeotropic orientations on surfaces presenting hydroxyl groups, the orientations of the UV-treated liquid crystal on the hydroxyl-terminated surface did not change with thickness of the film of liquid crystal in the manner observed on the ammonium-terminated surfaces. The latter result indicates that the mechanism leading to homeotropic anchoring on hydroxyl-terminated surfaces is distinct from that on ammonium-terminated surfaces. Measurements performed using polarization modulation infrared reflection-absorption spectroscopy suggest that hydrogen bonding between the 4-cyano-4'-biphenylearboxylic acid and the hydroxyl-terminated surface is responsible for the homeotropic anchoring on the surface. Finally, the orientation of the liquid crystal on methyl-terminated surfaces was not influenced by the addition of 4-eyano-4'-biphenylcarboxylic acid nor UV treatment. These results illustrate how the chemical composition of liquid crystals can be manipulated to achieve control over their ordering on surfaces that possess chemical functionality relevant to the development of liquid crystal-based sensors and diagnostic tools. We illustrate the utility of this approach by using the tailored liquid crystal to amplify and optically transduce the presence of proteins arrayed on ammonium-terminated surfaces. (c) 2006 Elsevier Inc. All rights reserved.
机译：我们报告了两种方法，其中涉及定制向列液晶4-氰基-4'-戊基联苯的化学组成，以实现对化学功能化表面上液晶的取向有序的控制。第一种方法涉及将4-氰基-4'-联苯羧酸直接加成到4-氰基-4'-戊基联苯中。第二种方法涉及将4-氰基-4'-戊基联苯暴露于紫外线下并光化学生成包括4-氰基-4'-联苯羧酸在内的一系列产品。酸的添加或紫外线的暴露加速了液晶在呈现铵基的表面上显示出从平面取向到垂直（垂直）取向转变的速率。经铵处理的表面上经UV处理的4-氰基-4'-戊基联苯的垂直取向的外观取决于液晶膜的厚度（13-50μm），这与液晶膜之间的偶极耦合一致液晶和与在铵表面产生的双电层相关的电场。尽管添加4-氰基-4'-联苯甲酸或液晶的紫外线处理也促进了具有羟基的表面上的垂直取向，但是在羟基封端的表面上经过紫外线处理的液晶的取向并未随厚度而变化。以在铵端基表面上观察到的方式测定液晶膜的厚度。后一个结果表明，导致在羟基末端表面上垂直锚固的机理不同于在铵末端表面上的垂直锚定。使用偏振调制红外反射吸收光谱法进行的测量表明，4-氰基-4'-联苯羧酸和羟基封端的表面之间的氢键是垂直于表面的锚定点。最后，液晶在甲基封端的表面上的取向不受4-eyano-4'-联苯羧酸的添加或UV处理的影响。这些结果说明了如何控制液晶的化学组成，以控制其在具有与基于液晶的传感器和诊断工具的开发有关的化学功能的表面上的排序。我们通过使用量身定制的液晶来放大和光学转导铵端基表面上排列的蛋白质的存在，说明了该方法的实用性。 （c）2006 Elsevier Inc.保留所有权利。

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