Hydrogen abstraction of carbon/phosphorus-containing radicals in photoassisted polymerization

Abstract

Free-radical-promoted photopolymerization has successfully improved the curing performance in cationic photopolymerization and is now employed in promoted autoxidation. The main objective was to investigate the photopolymerization kinetics of free-radical-promoted autoxidation by observing the effects of technological parameters such as the light intensity and the sources of the radicals on the rate profiles. The mechanisms of the reaction of a model alkyd monomer with a carbon-containing radical/phosphorus-containing radical, respectively, were also studied by density functional theory. The results showed that the reaction proceeds via hydrogen abstraction. The geometry of the transition states was simply analyzed in terms of a statistical thermodynamics method. A distortion/interaction model was used to understand the differences in energy between two transition states and helped to explain why the phosphorus-containing radical is highly reactive. A bond energy-bond order model and an Evans–Polanyi factor are available for analyzing the non-linear transition states in the carbon-containing radical system. Based on the results of quantum chemistry, Eyring transition state theory with the Wigner correction was employed to compute the pre-exponential factors and rate constants of the two reactions.