Atomistic modeling of bond exchange reaction and self-healing mechanisms in epoxy vitrimers

Epoxy-based vitrimers represent a promising class of covalent adaptable networks that offer a sustainable alternative to traditional thermosets by combining structural robustness with reprocessability and intrinsic self-healing. However, the molecular-level mechanisms underlying these dynamic functionalities remain insufficiently understood. In this study, we develop a large-scale molecular dynamics framework to model the curing and bond exchange processes in vitrimers synthesized from diglycidyl ether of bisphenol A (DGEBA) and 4-aminophenyl disulfide (4-AFD). A custom curing algorithm enables the construction of crosslinked networks with controlled crosslink densities (ρ_cl), allowing us to systematically evaluate the impact of network topology on mechanical and thermal properties. Our simulations reveal that increasing ρ_cl enhances the glass transition temperature, elastic modulus, and ultimate strength, due to reduced segmental mobility and a denser network structure. Crucially, we show that the incorporation of dynamic disulfide bonds enables thermally activated bond exchange reactions that effectively heal both nanovoids and preexisting cracks. The self-healed vitrimer recovers over 95% of its original mechanical performance, demonstrating the efficacy of network reconfiguration at the atomic scale. These findings provide mechanistic insights into the interplay between network architecture and vitrimer functionalities that are inaccessible by experiment alone. Our computational framework offers predictive capabilities for guiding material design and optimizing vitrimer performance for recyclable, reprocessable, and damage-tolerant polymer systems.