Photoinduced Cooperative Orientation and Pattern Formation in Copolymer Films with 4-Methoyazobenzene and Benzoic Acid Side Groups

Photoinduced cooperative molecular reorientation in liquid crystalline (LC) methacrylate copolymers with hexamethylene spacer groups terminated with 4-methoxyazobenzene and benzoic acid in the side chain, and the influence of the copolymerization ratio on the thermally enhanced photoinduced molecular reorientation behavior were investigated. All copolymers exhibited a LC phase, and sufficient thermally enhanced photoinduced in-plane molecular reorientation was achieved by irradiating with linearly polarized (LP) UV light and subsequent annealing when the azobenzene composition was greater than 5 mol%. Adjusting the exposure energy and the polarization of the LPUV light attained a patterned oriented structure, which can be useful as alignment layer for functional materials. Finally, a patterned birefringent film was fabricated using photocurable liquid crystals on the patterned copolymer film.