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

Abstract

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 (Hbond) 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 crosslinked 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.