Investigating the growth of hyperbranched polymers by self-condensing vinyl RAFT copolymerization from the surface of upconversion nanoparticles

Hyperbranched poly(N-(2-hydroxypropyl) methacrylamide)s grafted on upconversion nanoparticles (UCNPs) were prepared by surface-initiated self-condensing vinyl RAFT copolymerization from the surface of UCNPs modified with a RAFT chain transfer agent. The effect of the grafting density in RAFT chain transfer agent on UCNPs and the concentration in transmer were investigated. The propagation of the polymerization was strongly affected by termination and transfer reactions associated with the high local concentration in propagating chains due to the immobilization of the polymer chains at the surface of UCNPs and increased number of active centers during the polymerization, but also to the hopping and rolling mechanisms related to the surface-initiated RAFT polymerization. The development of such nanohybrids opens the way to novel nano-objects for biomedical imaging and theranostics.