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

ABSTRACT 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 poly(aryl amide)–polyurea (PA–PU) plastics obtained by copolymerizing rigid PA and flexible 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 (CFs) 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.