This paper describes the thermally enhanced in-plane alignment and other properties of liquid crystalline (LC) copolymers (1, 2, and 3) consisting of a methacrylate with a 2-styrylpyridine side group as a photocyclodimerizable group and a methacrylate with a methoxy biphenyl side group as a mesogenic group. $^1H$ NMR spectroscopy indicated that the contents of the photoreactive monomer unit in copolymers 1, 2, and 3 were 0.65, 0.46 and 0.19 (mole fraction), respectively. The copolymers in the film showed a transmittance of 92% at wavelengths > 450 nm, even at $100^{circ}C$, as well as thermal stability up to approximately $360^{circ}C$. Copolymers 1 and 2 gave a nematic texture at 155 and $150^{circ}C$, respectively, while copolymer 3 showed a smectic texture at $130^{circ}C$. The copolymer films aligned parallel to the linearly polarized UV(LPUV) light after LPUV light irradiation and subsequent thermal annealing. The respective in-plane order parameters of copolymers 1, 2, and 3 in the film at 315 nm were 0.65 at $0.001;J/cm^2$, 0.59 at $0.01;J/cm^2$, and 0.48 at $0.025;J/cm^2$ by the same treatment in the LC temperature ranges. This suggests that the photoreactive LC copolymers not only have high optical transparency and good thermal stability but also have controllable, high in-plane alignment with the contents of the photoreactive monomer unit.