Reusable Polyphenol Building Blocks Enable Recyclable Epoxy-Amine Thermosets via Methanolysis.

Biobased polyphenols represent attractive alternatives to bisphenol A for epoxy thermosets, yet most bio-derived epoxy networks remain permanently cross-linked and are difficult to recycle. Herein, we report a modular molecular design strategy that converts renewable polyphenols into reusable functional building blocks for recyclable epoxy-amine thermosets. Distinct from conventional degradable epoxy networks, this platform enables systematic structural variation and establishes a clear structure-depolymerization relationship. Kinetic and computational analyses further support a previously unrecognized ether-assisted methanolysis mechanism, in which neighboring ether functionalities and a favorable aliphatic amine environment lower the apparent kinetic barrier and modulate the local methanol environment around the cleavable ester bonds in a configuration-dependent manner. Consequently, the resulting thermosets undergo efficient methanolysis under mild conditions (70°C), affording reusable molecular components while maintaining tunable thermal and mechanical properties. Furthermore, carbon fiber-reinforced composites based on the optimized formulation can be efficiently depolymerized, yielding intact fibers and reusable building blocks in 88% isolated yield. The recovered polyols can be further upcycled into antibacterial quaternary ammonium materials, demonstrating a value-added reuse pathway. This work identifies a previously unrecognized molecular promotion mechanism for catalyst-free methanolysis and translates this mechanism insight into a structural design principle for recyclable polyphenol-based epoxy-amine thermosets.