Grafting of hyperbranched polymers onto ultrafine silica: postgraft polymerization of vinyl monomers initiated by pendant initiating groups of polymer chains grafted onto the surface

The grafting of polymers having pendant peroxycarbonate groups onto ultrafine silica surface and the radical postgraft polymerization of vinyl monomers initiated by the initiating groups of polymer chains grafted onto silica surface were investigated. The grafting of polymers having pendant peroxycarbonate groups onto the silica surface was achieved by the copolymerization of vinyl acetate (VAc) with t-butylperoxy-2-methacryloyloxyethylcarbonate (HEPO) initiated by azo groups introduced onto silica surface: the introduction of azo groups onto silica surface was achieved by the reaction of 4.4'-azobis(3-cyanopentanoic acid) with amino groups previously introduced onto the surface. The percentage of grafting (the proportion of grafted polymer to silica) of poly(VAc-co-HEPO) onto the surface was about 51% at 80.0 degreesC after 3 h. The amount of pendant peroxycarbonate groups of grafted chain was determined to be 0.55 mmol/g. Radical postgraft polymerization of various vinyl monomers, such as methyl methacrylate, glycidyl methacrylate, 2-hydroxyethyl methacrylate, vinyl acetate, and N-vinyl-2-pyrrolidinone was initiated by the pendant peroxycarbonate groups of grafted poly(VAc-co-HEPO) to give the corresponding hyperbranched polymer-grafted silica. It was found that the grafting of hydrophilic or hydrophobic polymers readily controls the surface wettability to water. (C) 2000 Elsevier Science B.V. All rights reserved.