Surface grafting of polyesters onto carbon nanofibers and electric properties of conductive composites prepared from polyester-grafted carbon nanofibers

Abstract

The grafting of polyesters onto carbon naonfiber, such as vapor grown carbon fiber (VGCF) and high density VGCF (HDVGCF), by the anionic ring-opening alternating copolymerization of epoxides with cyclic acid anhydrides initiated by potassium carboxylate (COOK) groups previously introduced onto these surfaces was investigated. The introduction of COOK groups onto these carbon nanofiber surfaces was successfully achieved by the neutralization of carboxyl groups with KOH. Carboxyl groups were introduced onto these surfaces by oxidation of these nanofibers with nitric acid and mixture of nitric acid with sulfuric acid. It was found that the anionic ring-opening alternating copolymerization of epoxides with cyclic acid anhydrides was successfully initiated by COOK groups on the surface to give the corresponding polyester-grafted carbon nanofiber. The dispersibility of carbon nanofiber in THF was remarkably improved by the grafting of polyesters onto the surface. The electric resistance of composite prepared from the polyester-grafted carbon nanofiber and polyethylene glycol) suddenly increased in methanol vapor over 103 times, and returned to initial resistance when it was transferred into dry air. These results indicate that the composite can be used as a novel gas sensor.