Key molecular structure determination of photoalignment materials from the effects of linearly polarized deep UV light on several polymers

We studied the photoalignment of nematic liquid crystals by examining polyimide, polyester, polystyrene, polyvinylalcohol (PVA), and polymethylmethacrylate (PMMA) exposed to linearly polarized deep UV (LPDUV) light. Polystyrene aligned the liquid crystal parallel to its LPDUV polarization axis, while polyimide and polyester aligned the liquid crystal perpendicular to the polarization axis. Polyimide and polyester exhibited order parameter peaks for small dosages of LPDUV. PVA and PMMA did not align the liquid crystal. The presence of a phenyl ring is a key to the decomposition-type photoalignment, whose alignment direction depends on the position of the phenyl ring. © 2000 Publication Board, Japanese Journal of Applied Physics.