Photoinduced anisotropy in spin-coated films of chiral smectic copolymethacrylates containing azobenzene side groups

Two copolymethacrylates containing the same phenyl benzoate side group but different azobenzene side groups were compared concerning their orientational behavior upon irradiation with linearly polarized (LP) light. Usually, the irradiation of azobenzene-containing copolymers with LP light at 488 nm results in the photoorientation of the azobenzene side group followed by the cooperative orientation of nonphotochromic side groups. The copolymethacrylates under investigation form stable optically isotropic IsoSmx phases at RT characterized by formation of a hidden layered liquid crystalline structure which is connected with the establishing of a helical superstructure. In this paper the competition between the establishment of the optically isotropic IsoSmx phase and the induction of anisotropy by LP light forcing a phase transition to a smectic structure will be discussed. The influence of the irradiation conditions, the thermal pre-history of the films, and the development of the order by annealing at 30 degrees C will be reported.