Molecular dynamics simulation and analytical investigations into dynamic crosslinking mechanism of epoxy asphalt

The crosslinking kinetics of epoxy asphalt (EA) present a potential path for improving performance and stability in various environmental conditions. The intricate connection between the evolution of molecular structure and mechanical properties during curing poses a significant hurdle for implementation. To address this issue, we applied atomic-scale molecular dynamics simulations to develop comprehensive profiles of EA at different degrees of crosslinking. By quantifying key metrics—interaction energy, radial distribution function (RDF), cohesive energy density (CED), and solubility parameter (δ)—we clarify how crosslinking regulates system stability, compatibility, molecular interactions, and network evolution. Concurrently, radius of gyration (Rg) and diffusion coefficient (D) reveal changes in network compactness. We find that increasing crosslinking yields a denser network mainly stabilized by van der Waals interactions, with limited electrostatic contributions. At 65.82 % crosslinking, the system reaches an optimal balance among compatibility, molecular interactions, diffusion behavior, and network structural evolution, representing the most stable microstructural state. Fourier transform infrared spectroscopy (FTIR) and fluorescence microscopy (FM) confirm that epoxy–anhydride ring-opening reactions dominate the curing process. Mechanical evaluations show that the stiffness–ductility balance is optimized at 35.62 % crosslinking in experiments, while simulations identify 44.63 % as the optimal point for strength–toughness, indicating that the best overall mechanical performance falls within this crosslinking interval. These insights establish a transferable molecular-level framework for predicting and optimizing the compatibility, diffusion capacity, and stiffness–ductility balance of EA at different crosslinking degrees, providing theoretical support and preliminary guidance for formulation design and material selection in engineering applications. • Atomic‑scale MD on EA models (5.83–98.42 % crosslinking) reveals dynamic crosslinking mechanisms. • Interaction energy, RDF, CED and δ analyses reveal good compatibility at 25.83 % and network stability at 65.82 %. • FTIR and fluorescence microscopy confirm epoxy–MTHPA ring‑opening curing and map morphological evolution. • Mechanical tests show optimal stiffness-ductility at 35.62 % and strength-toughness at 44.63 %, guiding molecular design.