High-Toughness and Intrinsically Self-Healing Cross-Linked Polyurea Elastomers with Dynamic Sextuple H-Bonds

High-performance elastomers that possess a combination of high mechanical toughness and fast healability have garnered extensive interest because of their diverse application potential. Inspired by the unique multiple hydrogen bond (H-bond) structure of spider silk and the rapid dynamic exchange of hindered urea bonds (HUBs), a self-healing polyurea elastomer with ultrahigh toughness was designed by incorporating dynamic sextuple H-bonds and HUBs into the polymer chain. Such a design affords high stretchability (1586%), excellent toughness (45.53 MJ m–3), good self-healing efficiency (91.6%), fracture energy (39.68 kJ m–2), and recyclability. The high mechanical performance and good healability are attributed to the presence of reversibly cross-linked noncovalent sextuple H-bonds and dynamically covalent HUBs, which have been validated by stress relaxation tests. Meanwhile, by substituting the chain extender adipic dihydrazide with hexamethylenediamine, which possesses a comparable structure but fewer amide bonds, the effect of sextuple H-bonds on elastomers was confirmed. More importantly, when a conductive layer of graphene oxide was applied to the surface of the resulting elastomer, the elastomers exhibited potential applications in strain sensors.