Surface Photografting Polymerization of Binary Monomers Maleic Anhydride and n-Butyl Vinyl Ether on Polypropylene Film II. Some Mechanistical Aspects

Abstract

On the basis of the previous work, another experiments were carried out to investigate the photografting polymerization of maleic anhydride (MAH)/ n-butyl vinyl ether (n-BVE) more intensively, from which some particular characteristics related to the mechanism were found out. The activation energy of the overall polymerization (Eap) is about 5.9 kJ mol-1, while the value of the photografting polymerization (Eag) is around 29.3 kJ mol-1, which indicates that high reaction temperature would reduce the homopolymerization and accordingly favors the graft polymerization. MAH, as a monomer, could act as a photoinitiator as well, which was deduced from the unexpected phenomenon that the photografting polymerization could perform smoothly even in the absence of photoinitiator. More experiments confirmed that the grafting efficiency reached the highest when the molar ratio of MAH to BVE was 1 : 1, from which it can be concluded that the formation of charge transfer complex (CTC) between MAH and BVE is a crucial factor leading to the high grafting efficiency. The formation of CTC was measured by UV spectra and the equilibrium constant of CTC was determined by 1H NMR method. As a result, the photografting process of the binary monomers MAH/BVE was outlined.