Photoorientation of liquid crystalline polymers and the influence of aggregation

The influence of molecular aggregation and liquid crystallinity on the phot oorientation of azobenzene side groups is studied in a series of LC polyacr ylates with different spacer length (x = 2-10). In the case of polymers wit h long spacers the process is restricted by the aggregation, but the restri ction can be overcome by a photochemical pretreatment irradiating with UV l ight or with Vis light of higher power density. After such a procedure the optical anisotropy increases with the spacer length caused by the higher mo bility and the higher ordering tendency of the polymers.