Functionalization of Silica Nanoparticles via the Combination of Surface-Initiated RAFT Polymerization and Click Reactions

A functional monomer with a pendant azide moiety, 6-azidohexyl methacrylate (AHMA), was polymerized on the surface of silica nanoparticles via surface-initiated reversible addition-fragmentation chain transfer (RAFT) polymerization with considerable control over the molecular weight and molecular weight distribution. The kinetics of AHMA polymerization mediated by 4-cyanopentanoic acid dithiobenzoate (CPDB) anchored nanoparticles was investigated and compared with that of AHMA polymerization mediated by free CPDB under similar conditions. The subsequent postfunctionalizations of PAHMA-grafted nanoparticles were demonstrated by reacting with various functional alkynes via click reactions. Kinetic studies showed that the reaction of surface-grafted PAHMA with phenylacetylene surface-grafted PAHMA was much faster than that of free PAHMA with phenylacetylene, whereas in the case of high molecular weight alkynes surface-grafted PAHMA showed lower reaction rates as compared to free PAHMA.