Azimuthal Anchoring Energy and Pretilt angle of Photo-aligned Nematic Liquid Crystals on a Polyimide and Poly(vinyl cinnamate) Blend Alignment Layer

摘要

The azimuthal anchoring energy and pretilt angle of a nematic liquid crystal (E7) which was aligned on a thin layer of polyimide (PI) and poly(vinyl cinnamate) (PVCi) blend by the irradiation of polar-ized UV on the surface, were studied. Within a PVCi content of 10~100 wt percent, the azimuthal anchor-ing energy remains unchanged with the decrease of the PVCi content in the blend, which is attributed to the preferential occupation of the surface by cinnamate chromophore. The blend alignment layer revealed a significantly enhanced thermal stability of azimuthal anchoring in comparison with the pie PVCi based alignment layer on account of the stiffening of the layer by the incorporated PI, which caused low thermal relaxation of the structural anisotropy developed from PVCi in the blend. The addition of PI into PVCi was also found to be effective for improving the thermal stability of the pretilt angle.