Effect of Photodimerization of Chalcone Moiety on the Temporal Stability of Optically Induced Birefringence in Photoresponsive Polymers Bearing a p-Methoxyazobenzene

We synthesized three methacrylate monomers containing chalcone moiety, mesogenic unit, and p-methoxyazobenzene chromophore, respectively. Copolymers and homopolymer were prepared using those monomers. Trans-to-cis photoisomerization was observed under the exposure of UV light using UV-Vis absorption spectroscopy. The kinetic study of trans-to-cis photoisomerization was performed in three different polymers. Reorientation of polar azobenzene molecules induced optical anisotropy under a linearly polarized light at 365 nm. Azobenzene unit underwent photoisomerization and photodimerization can be achieved in chalcone moieties under the same range of wavelength of light. Reorientation of azobenzene molecule was observed followed by photodimerization of chalcone moieties. Regarding the optically induced birefringence, the temporal stability was monitored without excitation light. Effect of mesogenic group and photodimerization on the temporal stability of photoinduced birefringence was studied.