Uniting Ultrahigh Performance with Complete Circularity in Biobased Hyperbranched Epoxy Resins

Abstract Epoxy resin thermosets are valued in critical aerospace and wind power applications for their excellent mechanical properties, thermal resistance, and chemical stability. However, their irreversible crosslinked networks make them difficult to recycle, resulting in substantial end-of-life waste. Achieving both ultrahigh performance and efficient circularity in epoxy resins remains a critical yet unresolved challenge. In this work, we report a high-performance biobased hyperbranched epoxy resin (PMEP-n) that synergistically integrates exceptional mechanical properties with complete circular upcyclability. By incorporating a hyperbranched architecture featuring imide and hexahydro-s-triazine units into a biobased epoxy system, the resulting PMEP-n resins substantially enhance the performance of conventional diglycidyl ether of bisphenol A (DGEBA). The optimized PMEP-12/DGEBA thermoset exhibits remarkable property improvements over neat DGEBA, including increases in tensile strength (48.1%), flexural strength (45.2%), impact strength (254.9%), and tensile toughness (131.9%). This enhancement is attributed to a uniform distribution of molecular pores and low free volume, resulting from tightly interpenetrating linear and hyperbranched polymer networks. Moreover, this high-performance material is designed for circularity, which can be degraded under mild conditions with a 95.2% recovery rate. Importantly, the degradation products are not merely recycled but upcycled, serving directly as a cocuring agent to fabricate new epoxy networks that outperform the original virgin resin, demonstrating 100% reusability and true closed-loop upcycling. This study establishes a novel strategy for developing sustainable epoxy resins that unite ultra-high performance with complete circularity, addressing the long-standing trade-off between material excellence and environmental sustainability.