In view of the complexity of surface photografting polymerization of vinyl acetate/maleic anhydride (VAC/MAH) binary monomer systems, a novel method was adopted in the present article to obtain insight into the relevant grafting copolymerization mechanism. This method includes two steps: sernibenzopinacol dormant groups were first introduced onto LDPE film by UV-irradiation and then thermally reactivated to produce LDPE macromolecular free radicals, which initiated the grafting copolymerization of VAC and MAH. It was demonstrated that, in the first step, the solvent used to introduce benzophenone (BP) to LDPE film largely affected the subsequent grafting copolymerization, which was closely related to the affinity of the solvent toward the substrate. The monomer feed composition had considerable influence on both the grafting and nongrafting copolymerization; however, the maximum copolymerization rates did not appear in the polymerization system with [VAC]/[MAH] being 1 : 1, but, in the system with a bit more VAC than MAH, as the total monomer concentration was raised, the maximum copolymerization rates tended to appear in the system with [VAC] equal to [MAH]. The relationship between the total copolymerization rate (RP) and monomer concentration was determined to be LnRP proportional to [VAC + MAH](1.83). All of these results indicated that both charge transfer (CT) complex formed by VAC and MAH and free monomers took part in grafting copolymerization. This feature differentiated the surface grafting copolymerization of VAC/MAH from the well-studied thermally induced alternating copolymerization of VAC/MAH. (c) 2005 Wiley Periodicals, Inc.