Liquid crystal alignment on periodic microstructure induced by single-beam 532 nm polarized laser illumination on poly(urethane-imide) film

After illumination by single-beam polarized pulse laser (532 nm) with energies below the ablation threshold energy, periodic microstructure was prepared on an azobenzene-containing poly(urethane-imide) (PUI) film surface. The reflective polarized IR results proved that the azobenzene group tended to be oriented perpendicular to the surface periodic microstructure. The illuminated PUI surface was used as the alignment layer of liquid crystal (LC) molecules. The experimental results indicated that the LC molecules tended to align closely along the surface microgrooves of the surface periodic microstructure. But the anchoring energy of LC molecules on the PUI film surface was smaller than that calculated based on the Berreman theory, which indicated that LC alignment on the laser-illuminated PUI film surface was controlled by the surface microgrooves and anisotropic orientation of the azobenzene group.