Grafting of Polymers onto Carbon Microcoil by Use of Carboxyl Groups on the Surface and Electric Properties of Conductive Composite Prepared from Silicone Rubber with the Polymer-Grafted Carbon Microcoil

Abstract

Carboxyl groups were successfully introduced on carbon microcoil (CMC) surface by the treatment with nitric acid. The carboxyl group content increased with increasing reaction time and reached to 1.34 mmol/g after 10 h. Poly(ethylene glycol) (PEG) was grafted onto the CMC surface by the reaction of carboxyl groups with terminal hydroxyl groups of PEG in the presence of condensing agent such as N,N′-dicyclohexylcarbodiimide or Lewis acid catalyst such as scandium (III) trifluoromethanesulfonate. Carboxyl groups on CMC surface have ability to initiate the cationic polymerization of vinyl monomers, such as isobutyl vinyl ether and N-vinylcarbazole and the corresponding polymers were grafted onto the surface. By grafting of polymers onto the surface, the entanglement of CMC was effectively destroyed and polymer-grafted CMC uniformly dispersed in good solvents for grafted polymer and silicone rubber. The inductance, capacitance, and resistance of conductive composite prepared from polymer-grafted CMC responded to acetone vapor. The inductance of the composite from polymer-grafted CMC increased in acetone vapor, and returned to initial value when it was transferred into air. The capacitance and resistance of the composite decreased in acetone vapor, and returned to initial value when it was transferred into air.