Synthesis, characterization and photoreaction of side‐chain liquid‐crystalline polymers comprising cinnamoyl biphenyl mesogen

Abstract Liquid‐crystalline (meth)acrylate monomers and polymers having mesogenic groups based on 4‐alkyloxy‐4′‐cinnamoylbiphenyl (m = 2, 6) were synthesized. The methacrylate monomers 4c, d were polymerized by free radical polymerization. Under the same conditions, the acrylate monomers 4a, b gave unidentified polymers in very low yield. To synthesize the acrylate polymer, the acrylate monomer having 4‐alkyloxy‐4′‐hydroxybiphenyl (m = 2, 6) was polymerized followed by the esterification of the hydroxy group using cinnamoyl chloride. All synthesized polymers having mesogenic moieties showed liquid‐crystalline phases in the high temperature range between 140°C and 245°C. The difference of aggregation of the cinnamoyl biphenyl mesogen among the polymers was studied by UV‐VIS spectroscopy at various temperatures. The photoreaction was performed in both solution and thin film. The [2+2] cycloaddition reaction preferentially occurred in the thin film although both [2+2] cycloaddition and photo‐Fries reactions could occur in the solution.