Synergistic Nanoconfinement and UV Crosslinking Enabling Self‐Strengthening, Ultra‐Robust Shape‐Memory Elastomers

ABSTRACT Fatigue‐induced degradation of mechanical properties remains a major challenge in achieving long‐term, reliable service of elastomers. We present a synergistic strategy that couples hydrazone‐linked covalent organic framework (H‐COF) nanoconfinement with UV‐triggered cross‐linking to realize self‐strengthening poly(urea‐urethane) (PUU) elastomers. H‐COF nanochannels provide abundant H‐bonding sites that immobilize chains and restrict mobility; upon UV irradiation, terminal C = C groups undergo confined radical polymerization within these channels, installing covalent cross‐links precisely in highly dynamic regions. This cooperative mechanism strengthens the network while preserving the dissipation of H‐bonds, yielding a 3.01× increase in tensile strength (85.1 MPa), a 2.10× enhancement in toughness (327.27 MJ•m − 3 ), and a 2.20× improvement in fracture energy (303.65 kJ•m − 2 ). Microstructural analysis reveals reduced domain spacing and homogenized morphology, while digital image correlation demonstrates suppressed strain localization. Moreover, UV irradiation shortens the shape‐memory recovery time (R r up to 99.06%) and intensifies fluorescence, providing a direct optical signal of the recovery process. This work establishes a generalizable design principle for stimuli‐programmed self‐strengthening under nanoconfinement, advancing elastomers toward adaptive durability.