Multi-scale simulations for predicting materials properties of a cross-linked polymer

In this paper we aim at predicting material properties of a cross-linked polymer by using multi-scale simulations and to compare the elastic properties and glass transition temperature with experimentally observed values. To that purpose we use an epoxy polymer for which the starting point is a mesoscopic simulation of its cross-linked structure realized by Dissipative Particle Dynamics (DPD) simulations, as recently improved to conserve local densities properly. This results in a coarse-grained structure of this thermoset polymer, relaxed at a large length- and long time-scale. Such a mesoscopic simulation is important as otherwise insufficient relaxation of the structures occurs for a later and proper comparison with experimental properties. Allowing further simulations at the atomistic scale using molecular dynamics (or any other method) to obtain material properties, a reverse-mapping procedure is required to insert atomistic detail into the coarse-grained structures. Hence, an efficient and reliable reverse-mapping procedure was implemented to be able to connect these two types of simulation. For the epoxy polymer chosen, Poisson’s ratio, the elastic modulus, the glass transition temperature and the thermal expansion coefficients of the glassy and rubbery state resulting from the equilibrated reverse-mapped structure, match the experimental values well. Overall, the paper reports a fast and straightforward procedure to bridge a mesoscopic structure to experimentally observed material properties, which can be applied to any system of interest