Alignment of liquid crystals on a photosensitive substrate studied by surface optical second-harmonic generation

Abstract

The adsorption kinetics and orientational ordering of 4Ј-n-octyl-4-cyanobiphenyl ͑8CB͒ liquid crystal films evaporated onto photosensitive poly͑vinyl-cinnamate͒ ͑PVCN͒ substrates were investigated by surface optical second-harmonic generation. The adsorption rate of the first monolayer decreases with increasing degree of photochemical modification of the polymer. The in-plane orientational anisotropy of the 8CB films grown on unidirectionally photopolymerized PVCN substrates is considerably lower than the intrinsic surface orientational anisotropy of these substrates, which can explain the generally found weak surface anchoring of liquid crystals on PVCN alignment layers.