Functionalization of multi-walled carbon nanotubes by free radical graft polymerization initiated from photoinduced surface groups

An easy method for preparing polymer-grafted multi-walled carbon nanotubes (MWCNTs) with high graft yields was developed by using free radical graft polymerization (FRGP) from photoinduced surface initiating groups on MWCNTs. The surface initiating groups were first formed by UV irradiation of MWCNTs previously modified with 2,2′-azobis[2-methyl-N-(2-hydroxyethyl)propionamide] (VA-086) (MWCNTs-OH) in the presence of benzophenone in benzene, and the subsequent FRGP of vinyl monomers was carried out consecutively at 80 °C. The surface initiating groups were homolytically cleaved to surface radicals and semipinacol radicals by thermal activation, and the surface radicals initiated FRGP. Polystyrene, poly(butyl acrylate), poly(methyl methacrylate), and poly(2-hydroxyethyl methacrylate) were successfully grafted onto the surface of MWCNTs with graft yields of 46, 26, 37, and 53 wt.%, respectively, after 15 h of FRGP.