Reprocessable Epoxy–Anhydride Resin Enabled by a Thermally Stable Liquid Transesterification Catalyst

Introducing dynamic ester bonds into epoxy-anhydride resins enhances the reprocessability of the crosslinked network, facilitated by various types of transesterification catalysts. However, existing catalysts, such as metal salts and organic molecules, often struggle with dispersion, volatility, or structural instability issues. Here, we propose to solve such problems by incorporating a liquid-state, thermally stable transesterification catalyst into epoxy resins. This catalyst, an imidazole derivative, can be uniformly dispersed in the epoxy resin at room temperature. In addition, it shows high-temperature structural stability above at least 200 °C as the synergistic effects of the electron-withdrawing group and steric bulk can be leveraged. It can also effectively promote transesterification at elevated temperatures, allowing for the effective release of shear stress. This property enables the thermal recycling and reshaping of the fully crosslinked epoxy-anhydride resin. This strategy not only enhances the functionality of epoxy resins but also broadens their applicability across various thermal and mechanical environments.