In accordance with the present disclosure, there is provided a solid state graft copolymerization process for the preparation of disentangled ultrahigh molecular weight polyethylene graft copolymers in which disentangled ultrahigh molecular weight polyethylene is admixed with at least one functional monomer and a free radical initiator to obtain a mixture; and the mixture thus obtained is subjected to solid state polymerization to obtain a graft copolymer of disentangled ultrahigh molecular weight polyethylene. The graft copolymers of disentangled ultrahigh molecular weight polyethylene shows better crystallization temperature that ranges between 117° C. to 121° C. and improved decomposition temperature (T100) that ranges between 460° C. to 480° C.