The cooperative molecular reorientation in methacrylate copolymer films comprising photoreactive 4-(4-methoxycinnamoyloxy)biphenyl and phenylester in their side chains was investigated by irradiation with linearly polarized ultraviolet light and subsequent annealing. Both cinnamate and phenylester side groups were miscible in the copolymer composition, and axis-selective photoreaction of the cinnamate groups was observed. Thermally enhanced cooperative in-plane orientation of both side groups was obtained when the irradiated films were annealed in the liquid crystalline temperature range of the copolymers.