关键词: 液晶, 取向, 偏振紫外光, 薄膜

Abstract: A kind of novel liquid crystalline oxetane monomers containing biphenyl, flexible spacer and cinnamoyl group was synthesized. The monomer was initiated to polymerize by boron trifluoride etherate and resulted in photoreactive polymer, which was highly sensitive to the LPL photochemically. The thermal properties and the mesophase structure of the polymer were investigated by DSC and thermal optical polarized microscope. Three exothermal peaks corresponding to an isotropic-nematic transition, nematic-smectic transition and smectic-crystal transition, respectively, were found on the DSC cooling curve of the polymer. Well-developed fan texture was observed by optical polarizing microscope. The polymer was spin-coated on a SiO₂ glass substrate from DMF solution, resulting in a thin film. Irradiation of a LP-UV light resulted in anisotropic cycloadditions of the cinnamon acyl groups, which caused the alignment of biphenyl groups in side chains at the same time. The differences of absorbance at different irradiation time were obtained which can be used to explain that the polymer can be applied in photoalignment layer.

Key words: Liquid crystal, Alignment, Polarized ultraviolet, Thin film