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Waveguide spectroscopic characterization of 3D anisotropies in conventionally photooriented and annealed films of liquid crystalline and amorphous azobenzene polymers

: Jung, C.C.; Rutloh, M.; Stumpe, J.


Journal of physical chemistry. B 109 (2005), No.16, pp.7865-7871
ISSN: 1089-5647
ISSN: 1520-6106
ISSN: 1520-5207
Journal Article
Fraunhofer IAP ()

Films of azobenzene-containing polymers were photooriented in the glassy state in such a way that the azobenzene side groups were oriented preferably perpendicular to the electric field vector. In the case of liquid crystalline polymers the photoinduced anisotropies generated in the glassy state were modified by thermotropic self-organization due to annealing above T-g. The conventional photoorientation process results in an oblate order. The changes in photoinduced anisotropies brought about by annealing in the liquid crystalline phase were investigated quantitatively for the first time by us for different polymer compositions and experimental conditions. Different biaxial and homeotropic orders result for liquid crystalline polymers, depending on the experimental conditions. Different polymer structures are compared and the influence of the interfaces is investigated. Orientational gradients can be induced by irradiation or annealing and are for the first time determined by the WKB (Wentzel-Kramers-Brillouin) method.