Self-Dynamics and Collective Swap-Driven Dynamics in a Particle Model for Vitrimers

We numerically investigate the self-dynamics and collective dynamics of a simple model for vitrimers-polymeric covalent networks that have the ability to dynamically rearrange the bond structure via exchange reactions, preserving the total connectivity. Specifically, we study a binary mixture of tetrafunctional and bifunctional particles by means of molecular dynamics simulations that naturally incorporate the bond-swapping mechanism. We specifically focus on the dynamics at small wavevector q by simulating 800 000 particles. We observe two distinct collective relaxation processes: (i) a fast vibrational damped mode and (ii) a slow network restructuring dynamics. Unexpectedly, the slow process is characterized by a wavevector-independent (q(0)) mode originating from the swap motion of the bonds.