Functionalization of carbon material by surface grafting of polymers

Recent advances in surface grafting of polymers onto carbon materials, such as carbon black, graphite powder, and carbon fiber, and the application of polymer-grafted carbon materials as a novel functional materials have been mainly reviewed. The grafting of polymers onto the surface was achieved by (1) grafting onto process, (2) grafting from process, (3) polymer reaction process, and (4) stepwise growth by dendrimer synthesis methodology. For the grafting, surface functional groups, such as carboxyl and phenolic hydroxy groups, were used as grafting sites. For example, in the living cationic polymerization initiated by carbon black/ZnCl2 system, carboxyl groups on the surface acted as initiating site and grafting site. In the surface grafting, polycondensed aromatic rings of carbon materials could be used as grafting sites by using ligand exchange reaction of polymers containing ferrocene moieties. It was demonstrated that, by the grafting of polymers onto carbon black surface, the dispersibility in solvent and the surface wettability were readily controlled by pH and temperature. By postgrafting of hydrophilic polymer to grafted hydrophobic chain on carbon black, amphiphilic carbon black was obtained. The applications of crystalline polymer-grafted carbon black as a novel gas sensor material and a positive temperature coefficient material are summarized.