Reusable Polyphenol Building Blocks Enable Recyclable Epoxy‐Amine Thermosets via Methanolysis

ABSTRACT 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.