Toward modulation of the naphthopyran photochromism: a miniemulsion copolymerization strategy

Abstract

Novel naphthopyran derivative based photochromic polymer nanoparticles are prepared via miniemulsion copolymerization with methyl methacrylate (MMA) and n-butyl methacrylate (BMA) monomers. The systematic modulation of the photochromic rate can be achieved via tuning the ratio of MMA and BMA monomers to lead the naphthopyrans to swing between rigid and soft surroundings. Transmission electron micrographs (TEM) and dynamic light scattering (DLS) images prove that the nanoparticles are discrete and smooth. The typical spectral characteristics of naphthopyran in the polymer nanoparticles indicate that the photochrome is incorporated into the nanoparticles successfully. In addition, the polymer nanoparticles exhibit good photochromic reversibility and stability upon UV irradiation and thermal back reaction.