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首页> 外文期刊>ACS applied materials & interfaces >Surface-Controlled Orientational Transitions in Elastically Strained Films of Liquid Crystal That Are Triggered by Vapors of Toluene
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Surface-Controlled Orientational Transitions in Elastically Strained Films of Liquid Crystal That Are Triggered by Vapors of Toluene

机译：甲苯蒸气触发的液晶弹性应变膜中的表面控制取向转变

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We report the fabrication of chemically patterned microwells that enable the rapid and facile preparation (by spin coating and patterned dewetting) of thin films of liquid crystals (LCs) that have precise thicknesses (0.7-30 mu m), are supported on chemically defined substrates, and have free upper surfaces. We use these microwells to prepare elastically strained nematic LC films supported on silica glass, gold, or polystyrene substrates and thereby characterize the response of the strained LC films to vapors of toluene. We report that low concentrations of toluene vapor (<500 ppm) can partition into the LC to lower the anchoring energy of the LC on these substrates, thus allowing the elastic energy of the strained LC film to drive the LC films through an orientational transition. The central role of the toluene-induced change in surface anchoring energy is supported by additional experiments in which the response of the nematic LC to changes in film thickness and substrate identity are quantified. A simple thermodynamic model captures these trends and yielded estimates of anchoring energies (8-22 mu J/m(2)). Significantly, the orientational transitions observed in these strained LC thin films occur at concentrations of toluene vapor that are almost 1 order of magnitude below those which lead to bulk phase transitions, and they are not triggered by exposure to water vapor. Overall, these results hint at principles for the design of responsive LC-based materials that can be triggered by concentrations of aromatic, volatile organic compounds that are relevant to human health.
机译：我们报告了化学图案化微孔的制造过程，该孔能够快速，轻松地制备（通过旋涂和图案化去湿法）具有精确厚度（0.7-30微米）的液晶（LC）薄膜，并被化学定义的基底支撑，并具有自由的上表面。我们使用这些微孔来制备负载在石英玻璃，金或聚苯乙烯基板上的弹性应变向列液晶膜，从而表征应变液晶膜对甲苯蒸气的响应。我们报告说，低浓度的甲苯蒸气（<500 ppm）可以分配到LC中，以降低LC在这些基底上的锚固能，从而允许应变LC膜的弹性能驱动LC膜通过定向转变。甲苯诱导的表面锚定能变化的中心作用得到了其他实验的支持，在该实验中，向列型液相色谱对膜厚和底物同一性变化的响应得以量化。一个简单的热力学模型捕获了这些趋势并得出了锚定能量的估计值（8-22μJ / m（2））。值得注意的是，在这些应变LC薄膜中观察到的取向转变发生在甲苯蒸气的浓度下，该浓度比导致本体相变的浓度低近1个数量级，并且不会因暴露于水蒸气而触发。总体而言，这些结果暗示了基于响应LC的材料设计的原理，这些原理可以由与人体健康相关的芳香，挥发性有机化合物的浓度触发。

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