Synthesis and optical properties of Azo-methacrylic copolymers with rigid tolane moiety

Methacrylic random copolymers bearing photoresponsive azobenzene (or azopyridine) and rigid tolane moieties as a side chains were synthesized and investigated on photoinduced birefringence (ΔnPI) characteristic for rewritable holographic memory application. Azobenzene (or azopyridine) segments were introduced as a functional group for a photo-triggered molecular reorientation. On the other hand, tolane segments were introduced for an improvement of transparency and practical photoinduced birefringence, which was defined as a performance index of photoinduced birefringence divided by absorbance of the film. As a result, the practical photoinduced birefringences of the copolymers have been improved significantly by an introduction of the tolane component compared to the azo homopolymers that have not any tolane component. Furthermore, the long-term stability of ΔnPI has been also improved by the introduction of the rigid tolane component.