Formation of grating by means of photoinduced alignment change of polymer liquid crystals with azobenzene moieties

We prepared a polymer liquid crystal (PLC) with ortho-substituted azobenzen e to explore the effect of the structure of the photochromic unit on the fo rmation of holographic grating. On this behavior, a remarkable difference w as observed between two materials, Grating formation of the ortho-substitut ed azobenzene moiety proceeded faster than that of common azobenzene analog s without substituents at the ortho position. This result is explained in t erms of the stability of the LC phase structure. We investigated the relati onship between alignment behavior and change of the diffracted light intens ity. The result shows that in the ortho-substituted azobenzene sample, the diffraction efficiency showed maximum when orientational relaxation is comp leted in a bright area of the interference pattern.