Photo-induced anisotropic films based on liquid crystalline copolymers containing stilbene units

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 T_g 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.