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Carbon Whisker as an Initiator of Cationic Polymerization of N-Vinylcarbazole and N-Vinyl-2-pyrrolidone

The cationic polymerization of vinyl monomers initiated by carbon whisker (vapor grown carbon fiber) was investigated. It was found that the cationic polymerization of N-vinylcarbazole (NVC) and N-vinyl-2-pyrrolidone (NVPD) is initiated by carbon whisker at 60–80°C. The activation energy of the polymerization of NVC was determined to be 56.5 kJ mol−1. During the polymerization, a part of the polymer was successfully grafted onto carbon whisker surface; the percentage of grafting of poly(NVC) in toluene at 60°C reached 89.3%. The percentage of grafting decreased with increase of polymerization temperature and increase of the dielectric constant of solvent. The initiating activity of carbon whisker considerably increased the further introduction of carboxyl groups onto the surface. By the blocking of surface carboxyl groups, carbon whisker lost initiating activity. Based on the above results, it was concluded that carboxyl groups on carbon whisker play an important role in the initiation of cationic polymerization. It was considered that polymerization is initiated by proton addition to monomer and that propagation proceeds with carboxylate anions on the surface as counter anions. The grafting of polymer onto the surface is due to the neutralization of the propagating cation with counter anion.