Photoinduced alignment of polymer liquid crystals containing azobenzene moieties in the side chain. 4. Dynamic study of the alignment process

An anisotropy was induced in initial isotropic (polydomain) polymer liquid crystal MACB-CNAB6 by using linearly polarized light at 366 nm. The alignme nt processes induced at various temperatures and various intensities of irr adiation light were analyzed by using a biexponential function (as shown in text). It was found that the alignment process involved two response modes : a fast response mode and a slow one. The fast response mode was associate d with the angular-dependent trans-cis photoisomerization and the prelimina ry alignment of mesogens, while the slow one was attributed to the position adjustment of the mesogens to obtain well-aligned monodomain. The writing rate and the induced anisotropy increased with increase in temperature and in light intensity at low intensity of the irradiation light. Combined with photochemical phase transition processes, optical switching and image stor age were realized in the polymer liquid crystal. (C) 1999 Elsevier Science Ltd. All rights reserved.