Surface photografting polymerization of vinyl acetate,maleic anhydride,and their charge‐transfer complex. VI. Charge‐transfer complex (2)

The photografting copolymerization of a low‐density polyethylene/vinyl acetate (VAC)–maleic anhydride (MAH) binary monomer system was studied from the perspective of dynamics. The total conversion percentage (CP) and grafting conversion percentage (CG) were measured by gravimetry. On the basis of plots of CP and CG as functions of the polymerization time, the total polymerization rate (RP) and grafting polymerization rate (RG) were calculated. In addition, the apparent activation energy (E_a) and the reaction orders of the photografting polymerization under different reaction conditions, such as the total monomer concentration and the concentration of benzophenone (BP), were determined also. The results showed that, in comparison with the photografting polymerization of the two single monomers (VAC and MAH), RP and RG noticeably increased for the VAC–MAH binary monomer system. When the total monomer concentration was kept at 4M, the apparent E_a's of the three photografting polymerization systems were as follows: for VAC ([MAH]/[VAC] = 0/4), E_a's for the total polymerization and grafting polymerization were 41.00 and 43.90 kJ/mol, respectively; for MAH ([MAH]/[VAC] = 4/0, E_a's were 39.65 and 43.23 kJ/mol, respectively; and for the VAC–MAH binary monomer system, E_a's were 34.35 and 40.32 kJ/mol, respectively. These results suggested that the polymerization of the binary system occurred more readily than the other two. The reaction orders of RP with respect to the total monomer concentration of the monomers and the concentration of BP were 1.34 and 0.81, respectively. According to these investigations, it could be inferred that in the binary monomer system, both the free monomers and charge‐transfer complex took part in the polymerization; to the termination of the propagating chains, two possible pathways, unimolecular termination and bimolecular termination, coexisted in this binary monomer system. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 910–915, 2005