A Coarse-Grained Model of Epoxy Network Polymers for Large Scale Molecular Dynamic Simulations

Epoxy resins are among the best matrix materials for many fiber composites. A coarse-grained (CG) model is developed to allow large-scale molecular dynamics simulations of epoxy network polymers based on EPON resin 862 and diethyltoluenediamine (DETDA). An all-atom model is first built for a small network of EPON chains crosslinked with DETDA crosslinkers. A systematic protocol based on chemistry-informed grouping of atoms, derivation of bond and angle interaction by fitting bond and angle distributions to Gaussian functions, and parameterization of nonbonded interactions by potential of mean force (PMF) calculations, is used to construct the CG model. An entropic correction term is introduced to the PMFs, which enables the resulting CG model to capture the thermal expansion property of the polymer and makes it transferable temperature-wise below the glass transition temperature. The CG model has been applied to explore the mechanical and structural properties of large epoxy networks and the results agree well with those from the all-atom model and experiments. Based on this CG model, a multi-cellular model is further developed to enable the modeling of epoxy network polymers at the micron size scale.