Molecular Dynamics Simulations of Photo-Induced Free Radical Polymerization

Curing kinetic models provide insight into how design parameters affect the kinetics of photopolymerization. However, they do not provide insight into how networks form or how they influence the process. This article describes a molecular dynamics simulation framework for simulating photoinitiated, chain growth, free radical polymerization. The framework was applied to simulate the photo-induced polymerization of bisphenol A (EO)10 diacrylate under varying conditions of curing light intensity and photoinitiator concentration. Results from the simulations agree very well with curing kinetic curves and gelation points derived from experiments. The simulations also reveal that: (1) gelation is highly correlated with the formation of giant molecules, (2) differences in the number of free radicals generated at the beginning of polymerization significantly affect polymer network formation at low to intermediate conversion, and thus affect the gelation point, and (3) increasing light intensity or photoinitiator concentration tends to delay the gelation point, but does not affect the ultimate polymer network structure near the latter stages of photopolymerization.