Analysis of Photoinduced Change in Properties on Macroscopic Motion of Crosslinked Azobenzene Liquid-Crystalline Polymers

Crosslinked azobenzene liquid-crystalline polymer films have been prepared by in-situ photopolymerization, and their photoinduced changes in birefringence and stress on macroscopic motion were investigated. Upon exposure to UV light, the film bent toward an actinic light source along the rubbing direction, and the bent film also reverted to the initial flat state after exposure to visible light at room temperature. Moreover, the birefringence simultaneously decreased and the stress was generated upon UV irradiation. These results indicate that the molecular alignment in the film becomes disordered by trans-cis photoisomerization of the azobenzene moieties and the resultant contraction of the film generates the stress.