Recyclable magnetic Fe3O4 supported photocatalyst for the metal-free ATRP

Silica layer coated Fe3O4 magnetic nanoparticles (Fe3O4@SiO2) were used to support an photocatalyst rhodamine B (RB) (Fe3O4@SiO2-RB) for the metal-free atom transfer radical polymerization (metal-free ATRP) of methyl methacrylate (MMA) for easy separation and recycling of the catalysts. The metal-free ATRP of MMA was carried out under 365 nm UV light using Fe3O4@SiO2-RB as photocatalyst, and ethyl 2-bromoisobutyrate (EBIB) as initiator. The structure of Fe3O4@SiO2-RB was demonstrated by FT-IR, XPS, XRD and TG. The changes of morphology and specific surface area of Fe3O4 before and after modification were observed by SEM and BET. For the metal-free ATRP reaction, the polymerization process was controllable, the molecular weight was uniform and end of the molecular chain was active. The Fe3O4@SiO2-RB catalyst can be recycled through simple magnetic separation to catalyze polymerization in a controlled manner for three times, and the catalytic activity of the three polymerization reactions decreased slightly in turn. The implementation of this strategy demonstrates that the photoinitiated catalysts can be recovered and reused for subsequent light-induced ATRP.