Radical graft polymerization from carbon whisker initiated by peroxyester groups introduced onto the surface

The radical graft polymerization of vinyl monomers onto carbon whiskers, i.e. vapor grown carbon fibers, initiated by tert-butyl peroxyester groups that are introduced onto the surface was investigated. The introduction of tert-butyl peroxyester groups onto the carbon whisker surface was achieved by the reaction of acyl chloride groups on the surface with tert-butyl hydroperoxide. The carbon whisker having acyl chloride groups was prepared by the following three methods: (1) reaction of surface carboxyl groups with thionyl chloride, (2) reaction of surface phenolic hydroxyl groups with succinyl dichloride, and (3) reaction of surface phenolic hydroxyl groups with phthaloyl dichloride. The carbon whiskers having tert-butyl peroxyester groups prepared from these three methods were abbreviated as CW-POE 1, 2, and 3, respectively. The peroxyester group content of CW-POE 1, 2, and 3 was determined to be 0.06, 0.05, and 0.17 mmol/g, respectively. It was found that the radical polymerization of vinyl monomers such as methyl methacrylate, styrene, and N-vinylcarbazole was successfully initiated in the presence of CW-POE 2 and 3, and the corresponding polymers were grafted onto the surface. However, CW-POE 1 failed to initiate the radical graft polymerization, because surface phenyl radicals formed by the thermal decomposition of the tert-butyl peroxyester groups are stabilized by the aromatic rings of the carbon whisker surface.