Crosslink network rearrangement via reactive encapsulation of solvent in epoxy curing: A combined molecular simulation and experimental study

Encapsulation of solvent during cure is proposed as one way to alter the network topology of crosslinked polymers. We performed all-atom molecular dynamics simulations to study systems comprised of Epon828 epoxy resin and Jeffamine-D400 diamine crosslinkers cured with varying amounts of the inert solvent dichloromethane (0–50 wt%) and then dried and annealed. Densities, glass transition temperatures, and Youngʹs moduli are observed to be insensitive to the initial amount of dichloromethane. These findings were verified by experiment. Simulations also showed that radial distribution functions and dihedral angle distributions were insensitive to the amount of dichloromethane present. However, using Dijkstraʹs algorithm, we observed that the distribution of minimum path lengths between crosslinks shifts appreciably to larger values as the amount of dichloromethane increases. This suggests that solvent-encapsulated curing can allow for control over network topology without changing crosslink density or intermolecular packing, and the properties derived from it, in highly crosslinked polymers.