Silica‐immobilized cumyl dithiobenzoate as mediating agent in reversible addition fragmentation chain transfer (RAFT) polymerization

Reversible addition fragmentation chain transfer (RAFT) polymerizations of styrene and methyl methacrylate were performed in bulk at 60°C, using cumyl dithiobenzoate as the mediating RAFT agent that has been immobilized via the stabilizing Z‐group to nanometer‐sized fumed silica particles. Increasing molecular weights with monomer conversion and absence of conventional polymerization activity in the interstitial solution phase were observed when the overall concentration of silica particles was carefully balanced with their respective cumyl dithiobenzoate loading. After completion of the polymerization, potentially sulfur‐free polymers with controlled molecular weights were obtained, initially via collecting the terminated polymeric material from the interstitial solution phase and, secondly, via cleavage of the surface‐confined polymer by a single addition fragmentation chain transfer step, which provides a pathway for recovery of the solid‐supported RAFT agent.