Photo/pH dual-responsive behavior of azopyridine-containing copolymer vesicles

The amphiphilic diblock copolymer composed of poly(ethylene oxide) as the hydrophilic chain and polymethacrylate with azopyridine moieties in the side groups as the hydrophobic chain self-assembled to vesicles in the mixture of THF/water. The dual photo- and pH-responsive behavior of the copolymeric vesicles was investigated by UV-Vis absorption spectra and optical microscope. It was found that the trans-cis photoisomerization of azopyridine in the vesicles was influenced by the water content in the mixture and the intensity of light irradiation. Regard to the pH-responsive behavior, the copolymer vesicles dissociated into solution gradually triggered by acid, while they reformed in a basic environment. Furthermore, the UV light irradiation accelerated the process of pH-induced dissociation of the vesicles.