Directed diffusion approach for preparing atomistic models of crosslinked epoxy for use in molecular simulations

A directed diffusion approach is used to create atomistic models of crosslinked epoxy. In polymerization-based approaches for preparing epoxy model structures, conversions higher than 95% are difficult to achieve due to very slow diffusion of unreacted monomers and crosslinkers in the partially formed network. This problem is overcome by creating very long bonds in the polymerization stage, and then relaxing these to equilibrium values by using a directed-diffusion-based relaxation strategy. The method minimizes the use of custom code by relying on the in-built functionality in LAMMPS package (S. Plimpton, J. Comput. Phys. 1995, 117, 1). The approach allows for near-complete conversion (≈99%) and the thermal and volumetric properties of the structures so prepared show good agreement with experimental data.