曝光量对含香豆素基团的液晶共聚高分子的光控取向性能的影响

本文设计合成了含有香豆素光敏基团的单体4-(6-丙烯酰氧基己氧基)苯甲酸-7-羟基香豆素酯(M1)和一种只含液晶基元的单体4-(丙烯酰氧基)己基苯甲酸-4-甲氧基苯酚酯(M2),并将这两种单体进行自由基聚合得到了共聚物.当该聚合物薄膜置于线性偏振紫外光(LPUV)下,会发生轴选择性的光化学反应,利用动态紫外光谱(UV光谱),对所合成的共聚物的光化学性能进行了研究.结果表明:当曝光能量为1740 mJ/cm²时,光反应达到饱和,紫外吸光度将不随曝光能量的变化而变化;随着曝光能量的增加,聚合物在反应初期光反应速率比较大,当曝光能量达到500 mJ/cm²左右,光反应度已经超过50%;当曝光量达到324 mJ/cm²,各向异性ΔA达到最大,ΔA_max=0.039.

The Effect of Exposure Energy on the Photoalignment of Liquid Crystals Using Coumarin-Containing Copolymer Film

In this article, two monomers were synthesized. One is with photosensitive group and another contains nothing but a mesogenic unit. Copolymer was obtained by free radical polymerization. When the copolymer film is exposed to the linearly polarized ultraviolet light (LPUV), it can generate a polarization-axis selective photoreaction. The photoalignment performance of the synthesized copolymer was tested preliminarily using dynamic UV spectrum. The results indicate that when the exposure energy gets to 1740 mJ/cm², the UV absorption do not change with the increasing of exposure energy. At the early stage, the rate of photoreaction is very fast. When the exposure energy is 500 mJ/cm², the degree of photoreaction is more than 50%. A large anisotropy ΔA_max=0.039 was generated when the exposure energy gets to 324 mJ/cm².