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

The grafting of polymers having pendant azo groups onto ultrafine silica surface and the radical postgraft polymerization of vinyl monomers initiated by the azo groups of polymer chains grafted onto the silica surface were investigated. The grafting of polymer having pendant azo groups was achieved by the reaction of 4,4'-azobis(4-cyanopentanoic acid) with pendant isocyanate groups of grafted polymer on silica surface. The grafting of polymer having pendant isocyanate groups was achieved by the copolymerization of methyl methacrylate (MMA) with 2-methacryloyloxyethyl isocyanate (MOI) initiated by silica having azo groups. The percentage of poly(MMA-co-MOI) became about 120% at 80degreesC after 2 h. The radical postgraft polymerization of vinyl monomers was initiated by the pendant azo groups introduced to poly(MMA-co-MOI)-grafted silica and hyperbranched polymer-grafted silica wag obtained. For instance, the overall grafting of poly(MMA-co-MOI) having polystyrene branch reached to 454.5%. It was found that the grafting of hydrophilic or hydrophobic polymers readily controls the surface wettability of silica to water. (C) 2002 Elsevier Science B.V. All rights reserved.