Experimental Investigations of Thin Free-Standing Liquid Crystal Films

在本研究中，我们使用了独特的交流自支撑膜量热技术来测量自支撑液晶膜和其他液晶介相的热容。这项技术可以研究二维物理现象，而不需要复杂的衬底效应。由于其极高的分辨率(优于1/100,000)，有可能从两层膜获得高质量的热容数据，并获得关于几种液晶化合物的近晶-A-六方B转变附近的意外的逐层转变序列的信息。此外，高分辨率光学反射率实验(优于5/10,0000)与量热测量相结合，以允许同时测量各种液膜和其他液晶中间相的热容和光学反射率。这项拟议的工作将使人们能够在二维检验与Kosterlitz-Thouless类型转变相关的重要理论预测，并将为二维无衬底系统的物理提供新的见解。%本研究开发的最先进的差动交流热计用于测量薄至两个分子层的独立液晶薄膜(类似于环上的肥皂膜)的热容。这种独特的技术为研究几个关键的二维物理现象提供了新的机会，而不会使衬底的影响复杂化。

In this research, the unique technique of differential ac free- standing film calorimetry is used to measure the heat capacity of free-standing liquid crystal films and other liquid crystal mesophases. This technique allows investigation of two-dimensional physical phenomena without the complicating effects of a substrate. Because of its extremely high resolution (better than 1 in 100,000), it is possible to obtain high-quality heat capacity data from the two-layer films, and acquire information on unexpected layer-by-layer transition sequence near the smectic-A-hexatic B transition of several liquid crystal compounds. In addition, high- resolution optical reflectivity experiments (better than 5 in 10,0000) are coupled to the calorimetric measurements to allow simultaneous measurements of heat capacity and optical reflectivity of various liquid films and other liquid crystal mesophases. The proposed work will enable one to test important theoretical predictions related to the Kosterlitz-Thouless-type transition in two dimensions, and will provide new insights into the physics of two-dimensional substrate-free systems. %%% A state of art differential ac calorimeter developed in this research is used to measure the heat capacity of free-standing liquid crystal films (similar to soap films on a ring) as thin as two molecular layers. This unique technique offers new opportunities to investigate several critical two-dimensional physical phenomena without the complicating effects of a substrate.