A visible light responsive azobenzene-functionalized polymer: Synthesis, self-assembly, and photoresponsive properties

A novel visible light responsive random copolymer consisting of hydrophobic azobenzene-containing acrylate units and hydrophilic acrylic acid units has been prepared. The azobenzene molecule bearing methoxy groups at all four ortho positions is readily synthesized by one-step conversion of diazotization. The as-prepared polymer can self-assemble into nanoparticles in water due to its amphiphilic nature. The tetra-o-methoxy-substituted azobenzene-functionalized polymer can exhibit the trans-to-cis photoswitching under the irradiation with green light of 520 nm and the cis-to-trans photoswitching under the irradiation with blue light of 420 nm in both solution and aggregate state. The morphologies of the self-assembled nanoparticles are revealed by TEM and DLS. The controlled release of loaded molecules from the nanoparticles can be realized by adjusting pH value since the copolymer possesses pH responsive acrylic acid groups. The fluorescence of loaded Nile Red in the nanoparticles can be tuned upon the visible light irradiation. The reversible photoswitching of the azobenzene-functionalized polymer under visible light may endow the polymer with wide applications without using ultraviolet light at all. (c) 2015 Wiley Periodicals, Inc.