Light-induced anisotropy of stilbene containing LC polymers and its thermal development by self-organization

The defined preparation of anisotropic films of functionalized polymers is important for different fields of optical applications. A promising way to create such films is based on the interaction of photochromic polymers with linearly polarized light. Different mechanisms are known to generate anisotropy. The best studied process is the photoorientation in the steady state of the E/Z photoisomerization of azobenzene moieties. But azobenzene based systems have some disadvantages. For this reason the light-induced orientation of photochromic liquid crystalline polymers without azobenzene moieties is presented. In the case of the studied photochromic LC polymers the light-induced anisotropy is used as a starting point for the thermal development of the order by a thermal post-orientation step based on the self-organization of LC polymers. This two-step orientation process combining a photoinduced and a subsequent thermal ordering process is a very promising way to orient efficiently LC polymers containing photochromic moieties. The light induced and the thermal developed order of four different polymers containing a mesogenic, a photochromic and a fluorescent stilbene side group were compared with respect to the composition of the polymers. This orientation procedure results in films with anisotropic fluorescence properties in the case of two of the investigated polymers.