Methacrylate polymer liquid crystals containing 4-(4-methoxycinnamoyloxy) biphenyl (MCB) side group with different alkylene spacer length between the polymethacrylate backbone and MCB side groups are synthesized. Influence of the alkylene spacer length on the thermally enhanced molecular reorientation behavior of thin films is investigated using linearly polarized ultraviolet (LPUV) light exposure and subsequent annealing. In-plane reorientation preferentially occurs when the alkylene spacer is short, and the induced in-plane order parameter is greater than 0.6. On the other hand, when the alkylene spacer is long, thermally induced out-of-plane reorientation is observed as well as the in-plane reorientation.