Photo-induced anisotropic films based on liquid crystalline copolymers containing stilbene units |
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Authors: | Raquel Giménez José Luis Serrano Ana I Viñuales Joachim Stumpe |
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Affiliation: | a Química Orgánica, Facultad de Ciencias-Instituto de Ciencia de Materiales de Aragón, Universidad de Zaragoza-CSIC, Pedro Cerbuna, 12, 50009 Zaragoza, Spain b Química Orgánica, Escuela Politécnica Superior de Huesca-Instituto de Ciencia de Materiales de Aragón, Universidad de Zaragoza-CSIC, 22074 Huesca, Spain c Fraunhofer Institute of Applied Polymer Research, Science Park Golm, 14476 Potsdam, Geiselbergstr. 69, Germany |
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Abstract: | New poly(methacrylate) copolymers containing 90 mol% of a promesogenic unit based on the 4-butoxybenzanilide, 4-cyanobiphenyl or 4-cyanoterphenyl cores and 10 mol% of a photosensitive push-pull substituted 4-(N-methylamino)-4′-nitrostilbene group have been prepared. All polymers are liquid crystalline and thermally stable with decomposition temperatures above 320 °C. The irradiation with linearly polarised light (either 325, 365 or 488 nm) results in the induction of a small optical anisotropy in the films due to an angular-selective photoreaction, whereas the absorbance perpendicular to the electric field vector of the incident light becomes larger compared to the absorbance parallel to it. In films of the copolymer containing 4-cyanobiphenyl and 4-(N-methylamino)-4′-nitrostilbene units, the anisotropy was significantly enhanced by annealing above Tg up to a dichroism D = 0.5. A thin film aligned by this procedure shows an anisotropic red emission with a ratio of 2.8 between emission intensities in the parallel and perpendicular directions due to the presence of oriented fluorescent stilbene units. |
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Keywords: | Liquid crystalline polymer Photoorientation Polarised luminescence |
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