Grafting of Polymers onto Carbon Black Surface by the Trapping of Polymer Radicals Formed by the Decomposition of Peroxide Polymers

Grafting reaction of peroxide polymers having pendant peroxycarbonate groups with carbon black surface was investigated. Peroxide polymers having pendant peroxycarbonate groups were prepared by the photo copolymerization of vinyl monomers with t-butylperoxy-2-methacryloyloxyethylcarbonate (HEPO) using 2,2′-azobisisobutyronitrile at room temperature. The grafting reaction of carbon black with the peroxide polymers was carried out at 100–110°C with stirring under nitrogen. Even if polymer having no pendant peroxide groups was heated with carbon black, no grafting of polymers onto the surface was observed. On the contrary, by the heating of the peroxide polymers with carbon black in toluene, the corresponding polymers were grafted onto the surface: the percentage of poly(methyl methacrylate-co-HEPO) grafting onto furnace black was determined to be 27.9%. The percentage of grafting tends to increase with increasing HEPO content of the copolymer. Based on the above results, it is suggested that polymer radicals formed by the thermal decomposition of pendant peroxycarbonate groups are trapped by polycondensed aromatic rings of carbon black. The grafting method according to the radical trapping by carbon black surface is useful for the grafting of polymers onto carbon black having few functional groups, such as furnace and acetylene black. Polymer-grafted carbon black gave a stable colloidal dispersion in good solvents for grafted polymer.