Photoresponsive Behavior of Heterocyclic Azo Polymers with Various Functional Groups

Here, we report on efficiency of light-induced processes in a series of methacrylic polymers containing heterocyclic azo moieties covalently attached to the polymer backbone. The optical response of the polymers was investigated in experiments on photoinduced birefringence measurements and surface relief gratings inscription upon irradiation with polarized blue light. The experimental results indicate that the presence of acceptor-type (Br) substituent in the side benzene ring linked to the heterocyclic ring has a beneficial effect on efficiency of birefringence generation, while incorporation of donor-type (CH3, OCH3) substituents lowers the level of photoinduced birefringence. Moreover, the process of surface relief structure formation was successfully observed for all studied polymers. The obtained surface-modulation depth reached up to 100 nm for two out of four investigated materials. No straightforward relation between the induced azo chromophore alignment level and the efficiency of mass-transport process is observed.