Grafting polymerization of methyl methacrylate (MMA) from vinyl modified silica mediated by 2-(2-cyanopropyl) dithiobenzoate was first conducted. Surface radicals generated by the addition reaction of "free" polymeric radicals with surface vinyl could initiate reversible addition-fragmentation chain transfer (RAFT) grafting polymerization of MMA from silica. The RAFT grafting polymerization of MMA from silica exhibited a living character, evident from the linear relationship of grafting ratio with monomer conversion. Grafting polymerization rate appeared dependent on target molecular weight and initiator concentration because of diffusion-controlled RAFT process on silica. The PMMA-grafted silica allowed for a second-step grafting polymerization due to the existence of dithioester group on the chain ends of grafted PMMA. In this case, surface radicals were generated by the reaction of "free" polymeric radicals with the surface RAFT agents, which differed from the RAFT process of grafting polymerization from vinyl modified silica. This method could be extended to prepare a variety of block copolymers from silica.

Keywords: grafting; radical polymerization; reversible addition-fragmentation chain transfer; surface modification; diffusion