Ouskova E, Reznikov Y, Shiyanovskii S V, Su L, West J L, Kuksenok O V, Francescangeli O, Simoni F
Institute of Physics, 46 Prospect Nauki, Kyiv, 03039, Ukraine.
Phys Rev E Stat Nonlin Soft Matter Phys. 2001 Nov;64(5 Pt 1):051709. doi: 10.1103/PhysRevE.64.051709. Epub 2001 Oct 24.
We show that adsorption of dye molecules control the light-induced alignment of dye-doped nematic liquid crystal (LC) on a nonphotosensitive polymer surface. The dependencies of light-induced twist structures on exposure, thermal baking, thickness, and aging before irradiation of the LC cells allowed us to propose the following mechanism for the alignment. Before irradiation, the "dark"-adsorbed layer on the tested surface is formed from dye molecules predominantly aligned along the initial direction of the director. Irradiation of the cell with linearly polarized light produces an additional layer with different orientational ordering of dye molecules. The final easy axis is determined by the competition of "dark" and light-induced contributions to anchoring and is aligned between the "dark" easy axes and polarization of the light. For quantitative interpretation, we apply the tensor model of anchoring and assume that the photoalignment in the mesophase is a cumulative effect of the light-induced anchoring on the background of the already existing anisotropic "dark" dye layer.
我们表明，染料分子的吸附控制了染料掺杂向列型液晶（LC）在非光敏聚合物表面上的光致取向。通过研究光致扭曲结构与液晶盒曝光、热烘烤、厚度以及辐照前老化的关系，我们提出了以下取向机制。在辐照之前，测试表面上的“暗”吸附层由主要沿指向矢初始方向排列的染料分子形成。用线偏振光照射液晶盒会产生一层具有不同取向有序性的染料分子附加层。最终的易轴由“暗”贡献和光致贡献对锚定的竞争决定，并排列在“暗”易轴和光的偏振之间。为了进行定量解释，我们应用了锚定张量模型，并假设中间相中的光取向是光致锚定在已存在的各向异性“暗”染料层背景上的累积效应。
