Multiscale interlinked structures limit fatigue crack propagation in a MXene-polyurethane composite

Self-healing materials hold significant commercial potential if their mechanical properties meet industrial requirements. However, conventional viscoelastic self-healing materials face an inherent compromise between fatigue resistance and stiffness, limiting their viability as substitutes for load-bearing rubber. To overcome this challenge, we construct multiscale structures, achieved through hydrogen bonding-driven assembly of a microscale transition metal carbide/carbonitride (MXene) framework within a self-healing polyurethane matrix featuring nanoscale continuous dynamic hard phase. This synergistic design endows the resulting composite with a fatigue threshold of 8226.3 J m⁻², modulus of 51.1 MPa, self-healing with 1 min recovery activated by near-infrared irradiation, and enhanced thermomechanical stability. Mechanism analysis reveals that the nanoscale continuous hard domains, coupled with the microscale MXene framework, collectively enable multiscale stress deconcentration while suppressing thermal activation effects in the composite. This study presents promising results for designing multifunctional, high-performance polymer composites via controlled multiscale structural coupling.