Photoinduced orientation of photoresponsive copolymers with N-benzylideneaniline and nonphotoreactive mesogenic side groups

The photoinduced reorientation behaviors of liquid crystalline (co)polymethacrylates (LCPs) comprised of N-benzylideneaniline (NBA) and 4-cyanobiphenyl or 4-methoxybiphenyl side groups are compared using linearly polarized (LP) 313 nm and LP 365 nm light. LCP films realize effective cooperative reorientation based on trans-cis-trans photoisomerization of the NBA moieties using LP 365 nm light and stabilization of the orientation structure due to copolymerization. In contrast, photochemical hydrolysis lowers the reorientation efficiency of LCP films when using 313 nm light. Changing the polarization direction of the LP 365 nm light controls the reorientation direction of the LCP films for several cycles, but the in-plane orientation order gradually decreases. Finally, LP 365 nm exposure and subsequent solvent annealing using a photo-cross-linked film achieve a repeatable write-erase-write of the orientation structure of the copolymer film.