Covalent adaptable networks (CANs) represent a transition material combining favorable features of thermosets and thermoplastics. However, it is still a huge challenge to simultaneously achieve fast reprocessability and high performance for CANs. Here, we designed catechol-based acetal CANs to achieve continuous reprocessing without sacrificing thermal and mechanical properties. A small-molecule model study demonstrated the significantly accelerated acetal exchange by neighboring group participation (NGP) of phenolic hydroxyl. Using this internally catalyzed acetal chemistry, a series of CANs with a broad range of properties were simply prepared from bio-based epigallocatechin gallate (EGCG) and tri­(ethylene glycol) divinyl ether (TEGVE) via one-step “click” cross-linking without using catalysts or releasing small-molecule byproducts. The dynamic nature of the CANs was confirmed via stress relaxation and multiple recycling methods including extrusion. While the dense cross-link density and high rigidity of the network provided high solvent resistance and mechanical properties. This work provides a promising and practical method to produce fast-reprocessing dynamic covalent polymer networks with dense cross-link density and superior performance.

Conventional polyurethane (PU) thermosets are built by nonrenewable petrifaction resources and are burdensome to be recycled, reprocessed, and reshaped in virtue of their permanent covalent cross-links. Here, for the first time, we synthesized a novel acetal precursor from abundant and renewable furfural and produced PU covalent adaptable networks (CANs) combining excellent reprocessability, controlled degradability, as well as outstanding high-temperature creep resistance. The properties could be further adjusted from soft to hard via the Diels–Alder reaction with bismaleimide. In addition, a small-molecule model study and theoretical calculations with density functional theory (DFT) certified that acetal linkage substituted by a furan ring (or a benzene ring) went through a dissociative exchange reaction via a carbocation mechanism. We envisage that the uncovering of the catalyst-free metathesis of acetal linkage substituted by a furan ring enriches the dynamic chemistry of acetal and greatly promotes the development of acetal-based CANs. Meanwhile, the acetal CANs provide a prime example to foster the development of advanced thermosets from renewable bioresources.