Self-Catalysis Highly Reversible Imidazole-Based Dynamic Covalent Polyurethane-Ureas

The reported dynamic covalent bonds (DCBs) exhibit certain drawbacks, including sluggish reaction rates and high dissociation temperatures, which impede the reusability of DCBs cross-linked polymers. Herein, we develop a kind of imidazole-urea bond (IUBs) through the rapid self-catalytic reaction between imidazole and isocyanate without additional catalysts. The IUBs are found to be highly reversible via a thermally dissociative mechanism while also demonstrating an irreversible exchange with amines. Then, histamine (1H-imidazole-4-ethanamine) is first employed as a chain extender to construct IUBs in the synthesis of novel imidazole-based cross-linked polyurethane-ureas (IMCPU). The IMCPU can undergo multiple recyclings of melt processing and be aminolyzed even at room temperature. Given the wide availability of the commodity histamine, IMCPU exhibits great potential for broad applications in the fields of dynamic materials.