The present invention is directed to a method of making a graft copolymer, comprising the steps of: obtaining a first polymer comprising at least one carbon-carbon double bond, the first polymer derived from at least one monomer, the at least one monomer comprising a conjugated diene monomer; polymerizing a second monomer in the presence of a thiocarbonylthio RAFT chain transfer agent to form a polymer comprising a terminal thiocarbonylthio group; cleaving the terminal thiocarbonylthio group to a thiol group to form the second polymer comprising a terminal thiol group; reacting the second polymer with the first polymer to form a graft copolymer, the graft copolymer comprising a backbone derived from the first polymer and sidechains derived from the second polymer.