Effect of Entanglements on Vitrimer Dynamics

The dynamics of polymer networks with associative bond exchanges, or vitrimers, are challenging to predict due to the interplay of the bond exchange reactions and the chain movement. While much work has explored the effect of bond kinetics and crosslink density, entanglements in vitrimer systems are relatively understudied despite their large effect on the rheological properties of traditional polymers. To gain insight into this interplay, we use coarse-grained molecular dynamics to simulate a polymer network consisting of tetra-functional crosslinkers separated by linear polymer chains with reactive end groups and backbone lengths above and below the entanglement threshold. For short, unentangled chains, the bond autocorrelation function follows a stretched exponential decay with an expected Arrhenius temperature dependence. For longer entangled chains, however, this simple behavior breaks down, and the relaxation is better described by a multi-step relaxation function. Further analysis of this difference in bond dynamics, as well as chain relaxation, will be discussed at various temperatures, demonstrating how entanglements contribute to the overall dynamics of the network.