The photo-reactive polymer was prepared by blending of poly(vinyl cinnamate) (PVCi) with alkanoyl cinnamic acid (ACA) which has been derived from 2-hydroxy cinnamic acid and alkanoyl chloride. The photo-alignment properties such as pretilt angle, azimuthal anchoring energy and the surface energy of the PVCi/ACA films were investigated by changing the alkyl chain length of ACA in the alignment layer. The exposure of polarized ultraviolet (UV) to the PVCi/ACA thin film induces the uniform homogeneous liquid crystal alignment. The pretilt angles increased with the alkyl chain length of ACA in the alignment layer. These changes may be greatly attributed to the polar and dispersion surface energy of the alignment layer. (C) 2001 Elsevier Science B.V. All rights reserved.