Coarse-grained Molecular Dynamics Simulation of Epoxy Network Polymers

Epoxy as an important type of thermosetting polymers has been widely used as matrix materials in polymer-based composites. To understand the thermomechanical response of such materials, we have developed a coarse-grained model of epoxy network polymers based on EPON resin 862 with diethyltoluenediamine (DETDA) as the curing agent, using a force-matching method coupled with chemistry-informed grouping of atoms into coarse-grained beads, direct Boltzmann inversion, and potential of mean force calculations between atomic groups. The model is used to construct a large epoxy network polymer and the mechanical moduli computed with the coarse-grained model are found to be close to the available experimental values and computational results from all-atom molecular dynamics simulations of a much smaller network. To further validate the coarse-grained model, the large coarse-grained network is backmapped to an all-atom one by replacing each coarse-grained bead with the corresponding atomic group. The mechanical properties of the large epoxy network with the all-atom representation are determined and compared with the results from the coarse-grained calculations. Furthermore, bond breakability is introduced to the coarse-grained network to enable the modeling of the fracture and crazing behavior of epoxy network polymers.