Alignment of liquid crystal molecules on UV-irradiated poly(vinylcinnamate) films

We have studied liquid crystal (LC) alignment on W-irradiated poly(vinyl cinnamate) (PVCi) films by texture observations and measurements of the anchoring energy. Irradiation of the PVCi films with linearly-polarized UV light creates optical anisotropy in the films and the anisotropy can align LCs well on these films. The alignment direction of LC molecules on the films is perpendicular to the polarization direction of the it-radiating UV light, which is shown to be due to the interaction of LC molecules and non-dimerized side-chains of PVCi molecules. LC molecules aligned on the film show an orientational transition phenomenon from homogeneous to homeotropic alignment as the temperature approaches a critical point. These observations indicate the critical weakening of the polar anchoring energy at the LC/PVCi interface.