Molecular Insights into Dynamic Relaxation in Vitrimers: Transesterification-Driven Self-Healing at the Atomistic Level.

Vitrimers are covalent adaptable networks that combine the structural stability of thermosets with self-healing enabled by dynamic covalent bonds. However, the molecular-level interplay among polymerization, prescribed bond-exchange reactions (BERs), finite-time mechanical relaxation, and nanoscale interfacial recovery remains incompletely understood. Here, we employ all-atom molecular dynamics simulations with the REACTER template-based reaction algorithm to construct a Bis-GMA/2-HEMA methacrylate polymer assembly and to model temperature-dependent transesterification. The resulting structure exhibits heterogeneous connectivity and a simulated glass transition temperature consistent with reported trends. With the imposed BER-acceptance window centered near the simulated Tg, mechanical and self-healing analyses reveal a model-conditioned temperature crossover. Near the glass transition region, BERs cooperate with emerging segmental mobility to accelerate finite-time mechanical relaxation and early-stage healing. At higher temperatures, thermally activated chain mobility and physical interfacial reconsolidation dominate the apparent response, making the incremental contribution of BERs secondary. Because the glass transition temperature and the topology-freezing temperature are distinct and the latter is not calculated here, the near-transition crossover is interpreted as conditional on the adopted BER schedule rather than as a universal vitrimer rule. These results clarify how dynamic covalent chemistry and temperature-controlled relaxation jointly regulate nanoscale vitrimer mechanics and repair within the accessible simulation window.