Surface Modification of Carbon Microbead by the Grafting of Polymers

The surface grafting of polymers onto carbon microbead, a sphere of carbonized phenol resin, was achieved by two methods: 1) the radical graft polymerization initiated by azo groups introduced onto the surface and 2) the trapping of polymer radicals by a carbon microbead surface. The introduction of azo groups onto a carbon microbead surface was achieved by the reaction of surface carboxyl groups on the bead with 2,2′-azobis[2-(hydroxymethyl)-propionitrile] using N, N′-dicyclohexyl-carbodiimide as a condensing agent. The radical polymerization of methyl methacrylate (MMA) was initiated by surface azo groups introduced onto the surface, and polyMMA was grafted onto the bead through the propagation of polymer chains from the surface: the percentage of grafting reached to 18% after 16 hours. Furthermore, it was found that by the reaction of an azo polyamide (a polyamide having an azo bond in the main chain) and peroxide polymers (polymers having peroxide groups in the main chain and/or pendant group) with carbon microbead at 70–110°C, polymer radicals formed by the thermal decomposition of these azo and peroxide polymers gave the corresponding polymer-grafted carbon microbead. The percentage of grafting decreased with increasing molecular weight of the polymer radicals. It was found that the reactivity of surface functional groups and polycondensed aromatic rings on carbon microbead are analogous with those of a carbon-black surface.