Synthesis of well-defined polymer brushes grafted onto silica nanoparticles via surface reversible addition-fragmentation chain transfer polymerization

Reversible addition-fragmentation chain transfer polymerization (RAFT) was used to prepare polymer brushes grafted onto silica nanoparticles. Novel RAFT-silane agents were prepared that contained both an active RAFT moiety and a silane coupling agent. RAFT agents were anchored to silica nanoparticles by the functionalization of colloidal silica with the RAFT-silane agents. RAFT polymerizations were then conducted from the particle surface to graft homopolymer and block copolymer brushes to the particles. The kinetics of styrene (St) and n-butyl acrylate (nBuA) surface RAFT polymerizations were investigated and compared with model polymerizations mediated by free RAFT agent. The molecular weights of grafted polymers increased linearly with conversions, and first-order kinetics were observed in the conversion range studied, indicating that the surface graft polymerization proceeded in a controlled manner. Well-defined PSt-block-PBuA copolymers attached to silica nanoparticles were also prepared.