The two-step method was employed to obtain insight into the grafting mechanism of (MAH-VAC)/LDPE film in the preceding investigation, where photoreduction of BP (the first step) was investigated and the subsequent grafting polymerization (the second step) was studied from the viewpoint of kinetics. The present article is devoted to investigation of the living polymerization performance, the compositions of the grafted chains, and the relevant grafting copolymerization mechanism of the (MAHVAC)/LDPE system. Both grafting copolymerization and nongrafting copolymerization performed living polymerization characteristics to some degree. Regarding the nongrafting copolymerization at a monomer concentration, [MAH] = [VAC] = 2M, MAH and VAC mainly underwent alternating copolymerization, especially at low temperatures; however, the grafting copolymerization mostly exhibited random copolymerization, which became obvious with the elevation of temperature. The composition of the monomer feed largely affected the composition of the grafted copolymer and the nongrafted copolymer. When [MAH]/[VAC] was either 2.5/1.5, 2/2, or 1.5/2.5, MAH/VAC in nongrafted copolymers stayed approximately at 1/1; while when [MAH]/[VAC] was 2.5/1.5, MAH/VAC in the grafted copolymer was nearly I / 1; but in the case of [MAH]/[VAC] being 2/2 and 1.5/2.5, the content of MAH in grafted chains was somewhat lower than that of VAC. All these results demonstrated that the grafting copolymerization on the substrate occurred randomly, which was greatly affected by the affinity of the monomer toward the substrate. This performance of the grafting copolymerization was much different from the nongrafting copolymerization in the solution. (c) 2005 Wiley Periodicals, Inc.