Robust yet deformable nanodomains for super-strong and ultra-tough reversibly cross-linked plastics

High-performance plastics that simultaneously integrate exceptional strength, modulus, toughness, and recyclability remain elusive owing to intrinsic property trade-offs. Here, we report super-strong and ultra-tough reversibly cross-linked PA-PU plastics obtained by copolymerizing rigid poly(aryl amide) (PA) and flexible polyurea (PU) chains. In situ-formed hydrogen-bonded PU nanodomains act as robust yet deformable cross-links, reinforcing strength of the plastics while efficiently dissipating energy through nanodomain deformation and hydrogen-bond dissociation. As a result, the PA-PU plastics exhibit a tensile strength of 103.7 MPa, a Young’s modulus of 2.5 GPa, and a toughness of 36.1 MJ m−3, along with satisfactory thermal resistance, chemical stability, and re-processability. Incorporation with carbon fibers produces PA-PU/CF composites with superior tensile and flexural properties, outstanding low-temperature impact resistance, and solvent-assisted recyclability, outperforming conventional epoxy/CF composites. This work establishes that in situ-formed nanodomains combining mechanical robustness with deformability offer an effective strategy to toughen plastics.