A healable waterborne polyurethane synergistically cross-linked by hydrogen bonds and covalent bonds for composite conductors

Elastomer materials integrated with high mechanical strength and excellent self-healing ability can be used as substrates in electronic skins, soft robots, and electrical devices. However, simultaneously enhancing the mechanical and self-healing properties of elastomers is still a great challenge because the self-healing ability of polymer materials is usually antagonistic to its mechanical strength. Herein, a novel healable polyurethane elastomer was developed using a double-network (DN) structure system. In the DN system, a loosely cross-linked chemical network was obtained via a photo-curable acrylic double bond, acting as a robust molecular framework and maintaining the elasticity of the polymer. Simultaneously, the physical cross-linked network produced by quadruple H-bonds of ureidopyrimidinone (UPy) units can not only achieve rapid reformation after fracture but also dissipate strain energy as a weak dynamic bond, endowing the elastomer with excellent self-healing ability and high stretchability. Owing to the accurate design, the synthesized elastomer exhibits excellent properties, including high tensile stress (13.71 MPa), high stretchability (similar to 500%), exceptional resilience and self-healing ability (90%). The robust healable elastomer enables the easy fabrication of composite conductors, which the prominent performance suggests as a great potential of the healable flexible sensor in next-generation wearable stretchable electronic devices, soft robots, and strain sensors.