From Steric Liability to Structural Asset: Non‐Benzylic Cation–π Anchoring Unlocks Hierarchical Hydrogen‐Bond Networks in Ultra‐Tough Recyclable Aromatic Polyurethane Elastomers

ABSTRACT Aromatic polyurethane elastomers offer intrinsic mechanical advantages, yet their bulky backbones are widely regarded as a steric liability that precludes the formation of ordered hydrogen‐bond networks essential for high toughness. This long‐standing conflict has consequently forced the field to rely on aliphatic precursors. To address this, we introduce thiabicyclononane‐pyridinium ionic crosslinkers to engage the aromatic hard segments through cation–π interactions. This strategy effectively transforms the inherent steric hindrance of benzene rings from an impediment into a potent driving force for assembling dense, hierarchical hydrogen‐bonded networks. The resulting elastomer (MA‐S) exhibits exceptional mechanical integration, featuring a high tensile strength of 60.3 MPa, an ultra‐high toughness of 283 MJ m −3 , outstanding impact resistance and a fracture energy of 198 kJ m −2 . These properties stem from the synergistic energy dissipation of hydrogen bonds, dynamic covalent bonds, and cation–π interactions. In addition, these multiple dynamic bonds endow the material with remarkable mechanical property retention (>95%) after multiple thermo‐compression cycles. Furthermore, the aromatic‐rich architecture enables robust π–π interfacial integration with carbon fibers, demonstrating a viable route toward closed‐loop recyclable structural composites. Consequently, this work establishes a versatile molecular design paradigm for creating sustainable, high‐performance polyurethanes that successfully reconcile mechanical robustness with dynamic recyclability.