Optical alignment and fixation of liquid crystals using azopolymer networks

Anisotropic gels of a nematic liquid crystal (NLC) were prepared using optical alignment and fixation in the absence of surface orientation layers. The method consists of first making a homogeneous mixture that contains a reactive diacrylate monomer bearing azobenzene group, a nonreactive NLC and a photoinitiator, then irradiating the mixture by a laser at lambda=532 nm for the liquid crystal (LC) orientation induction. Subsequently, the mixture is exposed by a second laser at lambda=350 nm for photopolymerization giving rise to anisotropic azobenzene network. Infrared dichroism measurements show that a remnant long-range LC orientation is retained by the network. (C) 2000 American Institute of Physics. [S0003-6951(00)04843-9].