Life-Cycle-Integrated Molecular Design of Hindered Phenylene Biacetal Epoxies for Practical Recyclable Composite Applications.

Carbon-fiber reinforced polymer (CFRP) composites are central to lightweight wind-energy infrastructure but suffer from poor end-of-life circularity due to permanent epoxy thermoset matrices. Here we present a life-cycle-integrated molecular design strategy for circular epoxy resins based on a hindered phenylene biacetal architecture, overcoming the longstanding industrial trade-offs between scalable synthesis, processability, high in-service performance, chemical recyclability, and long-term stability. The resins are prepared through one-pot scalable synthesis (≥200 g), producing liquid monomers compatible with vacuum-assisted resin infusion molding (VARI) with processing windows exceeding 60 min at 55°C. The resulting networks exhibit strong thermal-mechanical properties (Tg = 119°C-136°C, tensile strength ≥72 MPa) and significantly improved impact resistance (+83% vs. commercial bisphenol A epoxy), together with excellent durability, including negligible creep at 180°C and stable properties after prolonged hygrothermal aging (60°C/90% RH, 32 days). Dormant dynamic acetal linkages enable weak-acid-triggered deconstruction at room temperature, allowing 100% nondestructive carbon-fiber recovery and >80% recovery of high-purity monomeric precursors. Artificial-intelligence-assisted life-cycle assessment indicates a 45%-56% reduction in cradle-to-grave CO2 emissions compared with conventional CFRP disposal, with a total resource reutilization/upcycling rate exceeding 92%. This platform provides a practical pathway toward circular structural composites for net-zero infrastructure.