Photoinduced Orientation of Photoresponsive Polymers with N‑Benzylideneaniline Derivative Side Groups

Axis-selective photoreaction, photoinduced orientation, and formation of surface relief (SR) gratings of liquid crystalline polymethacrylates comprised of N-benzylideneaniline (NBA) derivative side groups are explored. Irradiating with linearly polarized (LP) 313 nm light generates molecular reorientation of the NBA side groups based on the axis-selective trans–cis–trans photoisomerization and photocleavage of the NBA groups. The in-plane order parameter (S) and birefringence (Δn) are ∼0.53 and ∼0.16, respectively. Furthermore, thermally stimulated amplification of the photoinduced optical anisotropy occurs upon exposing films to LP 313 nm light and subsequently annealing in the liquid crystalline temperature range of the material. The amplified S and Δn values are ∼0.71 and ∼0.21, respectively. Finally, polarization holography using 325 nm He–Cd laser beams with various interferometric polarization conditions demonstrates the formation of SR gratings with a molecularly oriented structure based on the periodic photoinduced reorientation and molecular motion.