(708c) Vinyl Ester Resin Crosslinking Using Molecular Dynamic Simulations

Molecular dynamics simulations on an atomistic scale were performed to create a series of crosslinked vinyl ester resins, where the crosslink density was varied at a constant degree of conversion. Thermodynamic and mechanical properties were obtained as a function of the crosslink density. In this study, a new algorithm was developed to generate the crosslinking network by incorporating the correct regioselectivity (head-to-tail chain propagation), and simulated the actual monomer reactivity ratios during the cure. These features had never been achieved in previous simulations. Most previous crosslinking simulations have been performed on epoxy resins, which undergo step-growth type polymerization. Vinyl esters, in contrast, cure by free radical chain polymerization. In this study, vinyl ester crosslinking networks with conversions up to 98% were successfully achieved. Volume shrinkage, glass transition temperature, and Young’s modulus of the equilibrated structures were calculated, where the resin’s crosslink densities were varied. The isotropic Young’s modulus was compared with available experimental data. This newly developed method holds great promise for generating other realistic thermoset and thermoplastic polymer systems containing two or more type of monomers.