Atomistic and Coarse-Grained Molecular Dynamics Simulations of Epoxy Network Polymers*

Polymer nanocomposites frequently rely on epoxy resins as matrix materials. Using chemistry-informed atom grouping, potential of mean force calculation, and a universal correction to the force field, we have developed a coarse-grained (CG) model of network epoxy polymers prepared with the EPON 862 resin (diglycidyl ether of bisphenol F) hardened by diethyltoluenediamine (DETDA). The CG model is used to construct an epoxy network polymer by directly modeling the crosslinking reaction process in a molecular dynamics (MD) simulation. The thermomechanical properties of the epoxy are computed with MD simulations based on the CG model. The CG network polymer is then back-mapped to an all-atom network and the polymer properties are determined again with atomistic MD simulations. A good agreement is found between the CG and all-atom results, confirming the validity of the CG model. The CG network polymers and the corresponding all-atom systems are used to compute various properties of epoxy polymers including mechanical moduli, thermal expansion coefficients, and fracture energies.