Photoinduced anisotropy in an azo-containing ionic liquid–crystalline polymer

Photoinduced anisotropy in an azobenzene ionic liquid–crystalline polymer was investigated through dichroism, birefringence and polarization holography. A dichroism degree of 1.58 and a birefringence value Δn ∼ 10−2 were achieved in the polymer film at room temperature, and the polymer film was found to possess the characteristics of reversible and long-term optical storage. Particularly the stored birefringence could be enhanced to Δn ∼ 10−1 by annealing the film, and it is attributed to the thermal self-organization of the molecules. Furthermore, linear- and circular-polarization holographic recordings were accomplished in the polymer film and pure polarization gratings were produced.