Dual-Function Enhancer for Near-Infrared Photopolymerization: Kinetic Modeling for Improved Efficacy by Suppressed Oxygen Inhibition

There are many strategies for improved conversion efficacy such as the reduction of oxygen inhibition effects (OIH). Three-component system using the phosphine to reduce the OIH effects during the free radical polymerization of (meth)acrylate monomers has been reported. Addition, near-infrared (NIR) photopolymerization offers advantages of safer, less light diffusion and scattering, and deeper penetration into the materials. This study presents the detailed kinetics, and modeling the conversion efficacy associated with the experimental results of Bonardi et al. (Macromolecules, 2018, 51, 1314-1324). The dual function of the enhancer additive includes: (i) regenerating the photoinitiator, and (ii) producing extra reactive radical. The temporal profiles of the concentration of each of the 3-component system and the associate conversion efficacy are numerically produced. In this study, several new findings showing unique features of various factors influencing the conversion will be demonstrated. For examples, reverse trends (roles) are found in: (i) the light intensity and enhancer concentration, and (ii) the coupling rate constants of radical-oxygen and radical-monomer. The monomer conversion is an increasing function of enhancer, oxygen concentration, and the light intensity. However, they have significantly different steady state features. The steady-state conversion increases from 10% without the enhancer (with enhancer concentration [B]
₀
= 0) to (30%, 50%, 80%) for [B]
₀
= (0.5, 1.0, 2.0)%. High conversion also requires a long lifetime of the free radical. Finally, the measured conversion profiles at various conditions reported by Bonardi et al. (Macromolecules, 2018, 51, 1314-1324) are compared and analyzed by our modeling.