Bridging Rigid Phases with Castor Oil-Based Soft Segments for Ultra-Strong and Chemically Recyclable Polymers and Their Fiber-Reinforced Composites

Developing plastics that integrate biomass-derived components while achieving high mechanical strength and recyclability remains a formidable challenge. Here, we report chemically recyclable COPI plastics fabricated by reversibly cross-linking low-molecular-weight boronic acid-terminated polyimide (BPI) with vinyl-diol-functionalized castor oil (VCO) through dynamic boronic ester bonds. The resulting soft-rigid hybrid networks, reinforced by reversible boronic ester linkages, hydrogen bonding, and π-π stacking, exhibit exceptional performance, including a tensile strength of ∼170.6 MPa, a Young’s modulus of ∼2.5 GPa, and a glass transition temperature of ∼217.6 °C. Benefiting from reversible boronic esters, COPI plastics can be selectively depolymerized in DMAc/ethanol to recover high-purity BPI and biodegradable VCO. Integrating COPI with carbon fibers yields CF/COPI composites whose mechanical properties rival CF/epoxy thermosets while maintaining chemical recyclability. This work demonstrates an effective strategy for creating ultrastrong, processable, and recyclable plastics and composites by reversibly cross-linking rigid and flexible segments through well-designed dynamic chemistries.