Photochemical switching behavior of liquid-crystalline networks: Effect of molecular structure of azobenzene molecules

Two types of photoresponsive liquid-crystalline (LC) networks with macroscopic uniaxial molecular orientation were prepared by polymerizing mixtures of a LC monoacrylate, a LC diacrylate and an azobenzene compound in a homogeneous glass cell at a nematic phase: one was the LC networks doped with azobenzene molecules and the other was those copolymerized with azobenzene monomers. The optical switching behavior of the LC networks was examined with respect to the molecular structure of the azobenzene molecules by using a Xe lamp and a single pulse light from a Nd:YAG laser as light sources. The LC networks doped with 4-butyl-4 ' -dodecyloxylazobenzene showed the fastest response time and decay time in the range of about 1.0 and 15 mus among the LC networks synthesized. The lateral intermolecular interaction as well as interaction through bonds affects significantly the optical switching behavior.