Synthesis and properties of photochromic spirooxazine with aggregation-induced emission fluorophores polymeric nanoparticles

We designed and synthesized photochromic fluorescent poly (MMA-co-SPO-co-TPE) nanoparticles with pendant spirooxazine (SPO) dye and tetraphenylethylene (TPE) fuorophores attached to poly (methyl methacrylate) (MMA) backbone by semi-continuous polymerization. The polymerization reactions were accomplished in water with randomly methylated-β-cyclodextrin (β-CD) at 80 °C in the presence of potassium peroxodisulfate which can be used as free radical initiator. This new synthetic method leads to uniform and smooth nanoparticles with a narrow particle size distribution. In addition, the poly (MMA-co-SPO-co-TPE) nanoparticles exhibit aggregation induced emission (AIE) properties and excellent photochemical properties because of spirooxazine dyes convert reversibly to merocyanine form upon ultraviolet (UV) irradiation, which active the intramolecular energy transfer pathway and quench the fluorescence of TPE in polymers. Consequently, the fluorescence of the poly (MMA-co-SPO-co-TPE) nanoparticles can be reversibly switched “on” and “off” upon UV and visible light, which maybe have potential application in biological fluorescent labeling as well as in optical fields like individually light–addressable nanoscale devices.