Influence of substituents on the reorientational behavior in photocrosslinkable polymer liquid crystal films with p-substituted cinnamoyloxybiphenyl side groups by irradiating with linearly polarized ultraviolet light and annealing

This paper describes the synthesis and influence of the substituent on the reorientation behavior of photocrosslinkable methacrylate polymer liquid crystals (PPLCs), which contain p-substituted cinnamoyloxybiphenyl (CB) side groups. Irradiating with linearly polarized ultraviolet (LPUV) light induced optical anisotropy of all PPLC films due to an axis-selective photoreaction of the mesogenic groups. The thermally enhanced reorientation direction depended on the substituent groups and liquid crystalline nature of the PPLC. A high in-plane reorientational order (S>0.6) parallel to the polarization of LPUV light was obtained for PPLCs with p-methoxy-CB and p-methyl-CB side groups, while out-of-plane reorientation was predominant for p-fluoro-CB and p-trifluoromethyl-CB side groups.