PURPOSE: The titled polymer useful in forming a neutral coating film layer on the surface of a polymeric material, prepared by aminating haloalkyl groups in the trunk polymer of a specified graft copolymer.

CONSTITUTION: Haloalkyl groups are aminated which are contained in a trunk polymer of a graft copolymer comprising, as the trunk polymer, a polymer containing structural units having haloalkylated aromatic ring pendants in the main chain (e.g., a polymer containing structural units such as haloalkylated styrene or halogenated vinyltoluene) and polyethylene oxide as a branch polymer. Thus, a graft copolymer capable of forming a neutral coating film layer on polymeric materials can be obtained. A coating film layer can be formed by immersing a polymeric material having cation exchangeable groups on the surface in an aqueous solution of the graft copolymer.