Thiol-vinyl mechanisms. 2. Kinetic modeling of ternary thiol-vinyl photopolymerizations

A framework is developed to understand and predict the photopolymerization kinetics of ternary thiol-vinyl systems: thiol-ene-ene and thiol-ene-acrylate. Ternary thiol-vinyl photopolymerization systems of thiol-allyl ether-norbornene, thiol-vinyl ether-norbornene, and thiol-vinyl ether-acrylate monomer mixtures are experimentally characterized and successfully modeled. The kinetic rate parameters employed for modeling are experimentally obtained from rotating sector unsteady-state analysis and rate mechanisms of the corresponding binary mixtures. In thiol-ene-ene systems, the relative consumption of the ene functional groups is shown to be proportional to the respective propagation kinetic parameters of the ene monomers and independent of the chain transfer kinetic parameters. In the thiol-ene-acrylate systems that exhibit a mixed step-chain growth mechanism, the relative conversion of monomers is shown to depend on both the propagation and chain transfer kinetic parameters.