Accelerated ReaxFF Simulations of Vitrimers with Dynamic Covalent Adaptive Networks

Vitrimers are a novel class of sustainable polymers with dynamic covalent adaptive networks driven by bond-exchange reactions between different constituents, making vitrimers reprocessable and recyclable. Current modeling approaches of bond-exchange reactions fall short in realistically capturing the complete reaction pathways, which limits our understanding of the viscoelastic properties of vitrimers. This research addresses these limitations by extending and employing the Accelerated reactive molecular dynamics (ReaxFF) technique, thus enabling a more accurate representation of vitrimer viscoelastic behavior at the molecular level. Bayesian optimization is employed to select force field parameters within the Accelerated ReaxFF framework, and an empirical function is proposed to model temperature dependence, thereby controlling the reaction probabilities under varying temperatures. The extended framework is employed to simulate nonisothermal creep behavior of vitrimers under different applied stress levels, heating rates, and numbers of reactions. The simulation results agree with experimental findings in the literature, validating the robustness of the framework.