Synthesis of Spiropyran Functionalized Polymer Nanoparticles and Investigation the Effect of Local Polarity on Kinetics of Photoresponsivity

The functionalized polymer nanoparticles were synthesized by emulsion copolymerization and then modified physically with spiropyran by post-polymerization modification method. The optical properties of the prepared photoluminescent polymer nanoparticles were studied by UV-Vis spectroscopy, which results indicated that photoresponsivity of spiropyran was influenced significantly by local polarity of functionalized polymer nanoparticles. In addition, investigation the kinetics of photoresponsivity of the spiropyran toward UV and visible light (by isomerization between two structures) displayed fast responsivity of spiropyran under UV irradiation for samples containing polar functional groups, and fast responsivity under visible light was recorded for samples with less polarity. Therefore, the spiropyran photoswitches have potential applications for photosensing of local polarity in functionalized copolymer nanoparticles, and also the photoluminescent nanoparticles containing spiropyran can be used as high security anticounterfeiting inks for printing of optical security tags on confidential documents.