Noncovalent functionalization of graphene with end-functional polymers

Stable dispersion of reduced graphene in various organic solvents was achieved via noncovalent functionalization with amine-terminated polymers. An aqueous dispersion of reduced graphene was prepared by chemical reduction of graphene oxide in aqueous media and was vacuum filtered to generate reduced graphene sheets. Good solvents and nonsolvents for the dried reduced graphene were evaluated using a solubility test. To achieve stable dispersion in the evaluated nonsolvents, amine-terminated polystyrene was noncovalently functionalized to the graphene, while graphene sheets were phase transferred via sonication from aqueous phase to the organic nonsolvent phase, including the amine-terminated polymers. Thorough FTIR and Raman spectroscopy investigation verified that the protonated amine terminal group of polystyrene underwent noncovalent functionalization to the carboxylate groups at the graphene surface, providing the high dispersibility in various organic media.