Novel Thermal Latent Curing Agents for Epoxy Resins Based on Dual-Locked Aminopyridines by Amidation and N-Oxidation

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Thermal latent curing agents are very important industrially because they can cure epoxy resins at a set temperature and can be stored as one-component systems. However, it remains difficult to achieve both a long pot life and high reaction efficiency. Herein, we present a dual-locked thermal latent curing agent based on aminopyridines, protected by amidation and N-oxidation, designed to enhance both pot life and final curing efficiency. We demonstrated that this dual-locked aminopyridine undergoes stepwise deprotection during the epoxy curing process, as evidenced by 1H NMR and MALDI-TOF MS analyses of model epoxy polymerizations. The curing temperature of epoxy resin with the dual-locked aminopyridines was modifiable within the range 120–154 °C, influenced by the electron density on the N-oxide. Furthermore, the dual-lock strategy was found to significantly improve the storage stability of one-component epoxy resins and promote the curing of epoxy with high efficiency compared to unprotected aminopyridines.