Coarse-Grained Molecular Dynamics Simulation of Filled Polymer Nanocomposites under Uniaxial Elongation

We performed coarse-grained MD simulations of polymer nanocomposites with spherical nanoparticles (NPs) on the basis of the Kremer-Grest model. Cases of "aggregated" and "dispersed" NPs are compared for repulsive and attractive interactions among the NPs and the polymers. Although a clear difference in the stress-strain relations for the interactions can be seen, a small dependence of morphological changes of positions of NPs is observed for a small mesh cross-linked polymer network. It is confirmed that the attractive interaction enhances the stress values as well as the degree of NP aggregation. For large elongation ratios, the bond orientation orders to the elongation axis are increasing. For the "aggregated" NPs, this increase is significant. We also calculated two-dimensional scattering patterns of NPs during the elongations. For strain >50%, we observed a spot pattern on structure factor S(q_x,q_yz) and a two-point bar pattern on scattering intensity I(q_x,q_yz), which have been reported in the experiments. A small dependence of the two-dimensional scattering patterns on the interactions can be observed as well as that of the NP configurations.