Thermal-Resistant One-Component Epoxy Resins Based on Synergistic Secondary Interactions between Lignin-Derived Triarylimidazole and Bismaleimide

One-component epoxy resins have attracted considerable interest due to their superior storage stability and processability, with advancements in their development being driven by chemical innovations aimed at regulating the thermal latency of epoxy curing systems. In this study, a preparation method for one-component epoxy resins was proposed, which is highlighted by the excellent storage stability, feasibility, renewability of feedstocks, and enhanced thermal resistance of the cured resin. Specifically, the curing system was composed of aromatic bismaleimide, lignin-derived triarylimidazole, and commercially available epoxy prepolymers. During the mixing stage, the electron-rich imidazole interacted with the electron-deficient maleimide, resulting in the formation of complexes through dipole interactions and π-π stacking. This interaction effectively sequestered the nucleophilic lone pair electrons and electrophilic epoxy groups, significantly improving the storage stability of the curing system at ambient temperature without the need for prepreparation of latent curing agents. As the temperature increased, the weak interactions diminished, releasing the active imidazole, which initiates the homopolymerization of the bismaleimide component and the epoxy component as well as their copolymerization. Consequently, a hybrid network that incorporates both bismaleimide and epoxy resins, with lignin-derived triarylimidazole serving as the linkages, was formed. The bismaleimide resin component substantially enhanced the thermal resistance of the hybrid resin, achieving a lap-shear strength of 3.31 MPa at 250 °C. These findings provide valuable insights for the advancement of one-component epoxy resins and exemplify the high-value utilization of lignin derivatives.