Interdependence of Photoorientation and Thermotropic Self-Organization in Photochromic Liquid Crystalline Polymers

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Abstract
By irradiation with linearly polarized light optical anisotropy is generated in isotropic films of photochromic LCP's due to a photoorientation process. Generally, the efficiency is much higher in films of polymers with a high content of azobenzene moieties. On the other hand, the photochemically induced orientation of the photochromic side groups affects also the distribution of non-photochromic but mesogenic moieties. Furthermore, in initially isotropic films it acts as initializing force, governing the direction of thermotropic self-organization. The combination of both ordering principles causes a significant amplification of the light-induced optical anisotropy. Investigating several polymers of the same general structure but with a different content of azobenzene side groups an interdependent behaviour was found for the photoorientation of the photochromic and the co-operative orientation of non-photochromic side groups.