Reprocessable and chemically recyclable poly(acylhydrazone-imine) covalent adaptable networks with enhanced mechanical strength and creep resistance

Chemical recycling of thermosetting resins represents a sustainable solution to deal with end-of-life polymer products in an energy-saving and easy-to-conduct way. However, it remains a major challenge to fabricate easy-to-achieve chemically recyclable thermosets that possess superior mechanical strength, high fracture toughness, and desirable creep resistance. Herein, a new chemically recyclable poly(acylhydrazone-imine) covalent adaptable network (CAN) is reported by systematically tailoring the intramolecular dynamic interactions of polymer networks. The introduction of acylhydrazone bonds endowed PAIx-CANs with both high mechanical strength and fracture toughness through the formation of synergistic hydrogen-binding interactions. For example, PAI1-CANs exhibit a high Young's modulus of similar to 1.58 GPa, a yield strength of similar to 83.7 MPa, a tensile strength of similar to 73.6 MPa, and also a high fracture toughness of similar to 19.7 MJ m-3. Meanwhile, owing to the strong intermolecular hydrogen-binding interactions, the obtained PAIx-CANs also exhibit good creep resistance. Interestingly, the PAIx-CANs can be depolymerized into the starting monomers in high purity under acidic conditions at room temperature. The recovered monomers can be further utilized to fabricate new PAIx-CANs with comparable mechanical properties to the original PAIx-CANs. This work provides a new method for the construction of high-performance chemically recyclable thermosets as next-generation substitutes for conventional thermosetting resins. A room temperature chemically recyclable poly(acylhydrazone-imine) covalent adaptable network with high mechanical strength and creep resistance was constructed by designing synergetic hydrogen bonds and acylhydrazone bonds in a single polymer network.