Energy dissipation after chain scission in polymer networks*

The fracture of end-linked polymer networks strongly affects the performance of these widely-used materials, but a fully quantitative understanding of the fracture behavior is still lacking. In recent years, theories built on the Lake-Thomas theory have emerged to predict the fracture energy by incorporating the effect of defects in the networks. However, experimental studies have suggested that the energy stored in each bond at the time of fracture (U) may be much smaller than the bond dissociation energy, which is a usual assumption in these theories. In this study, we perform molecular dynamics (MD) simulations to model end-linked polymer network systems and analyze the energy dissipated during fracture. Previous studies in our group have shown that a loop-modified Lake-Thomas theory successfully predicts the fracture properties of polymer networks without any adjustable non-physical parameters, but questions around the choice of U remain. Additionally, a dependence of the energy dissipated per bond on the polymer strand length is observed. In this talk, I will describe our simulations attempting to uncover how the energy dissipated depends on the polymer strand length, the network volume fraction, and defect concentration in the network.