INVESTIGATION OF SURFACE-INDUCED ALIGNMENT OF LIQUID-CRYSTAL MOLECULES BY OPTICAL 2ND-HARMONIC GENERATION
INVESTIGATION OF SURFACE-INDUCED ALIGNMENT OF LIQUID-CRYSTAL MOLECULES BY OPTICAL 2ND-HARMONIC GENERATION
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DOI：
10.1103/physreva.43.6778
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发表时间：
1991-06-15
影响因子：
2.9
通讯作者：
SHEN, YR
中科院分区：
文献类型：
--
作者：
FELLER, MB;CHEN, W;SHEN, YR
我们应用光学二次谐波产生技术来研究均匀排列液晶盒。该技术的表面偶极灵敏度使得有可能在不存在和存在大量液晶的情况下研究单层。通过比较三种表面处理（摩擦聚合物涂层基板、摩擦表面涂层基板和倾斜蒸发SiO（x）膜基板）的单层取向分布函数，我们发现两种不同的表面起源机制对液晶薄膜的取向是有效的。对于摩擦的聚合物样品，它示出，短程分子相互作用是负责的第一单层，然后通过epitaxylike相互作用对齐的散装对齐。结果与各种结构和组成的聚合物和摩擦与各种摩擦强度。对于其他表面处理，第一单层是各向同性分布的，这表明，体弹性相互作用是负责散装对齐。
We apply the technique of optical second-harmonic generation to study homogeneously aligned liquid-crystal cells. The surface dipole sensitivity of the technique made it possible to study the monolayer in the absence and presence of a bulk of liquid crystal. By comparing the monolayer orientational distribution functions of three surface treatments (rubbed polymer-coated substrates, rubbed surfactant-coated substrates, and substrates made from oblique evaporation of SiO(x) film), we find that two different surface-originated mechanisms are effective in aligning liquid-crystal films. For rubbed polymer samples, it is shown that a short-range molecular interaction is responsible for alignment of the first monolayer, which then aligns the bulk via an epitaxylike interaction. Results on polymers with various structures and compositions and rubbed with a variety of rubbing strengths are presented. For the other surface treatments, the first monolayer is isotropically distributed, indicating that a bulk elastic interaction is responsible for the bulk alignment.