Dual-hard phase structures make mechanically tough and autonomous self-healable polyurethane elastomers

• A novel strong autonomic self-healing elastomer is designed. • Dual-hard phase structure is realized by introducing dangling fatty acid chains. • Plasticizing segments with hard crystalline domains to address this dilemma. • Self-healable elastomer behaves simultaneously high strength and great toughness. • Auto-repairing conducting devices are demonstrated using developed elastomer. It is a key challenge to combine high mechanical strength and excellent autonomous self-healing properties in one elastomer to match the requirements of commercial applications. Chemical cross-linking or crystalline domains can afford high mechanical strength but are often based on the cost of losing autonomous self-healing performance. To address this dilemma, a strategy involving dual hard phase structures was developed to reinforce self-healing polyurethane elastomers, by introducing plant oil-derived fatty acid side chains into the hard segments. The dangling fatty acid chains not only allow segmental motion of the hard domains but also suppress the crystallization within polyurethane soft segments. The synergistic dual-hard phase structure and dynamic chain motion are responsible for outstanding mechanical properties (tensile strength to 21.8 MPa and toughness of 131.6 MJ m -3 ) and autonomous self-healing ability (∼100% healing efficiency). Furthermore, a versatile mechanical robust flexible conductor is conveniently constructed with an auto-repair capability at ambient conditions. This work represents a molecular design paradigm of simultaneously integrating balanced mechanical strength, durability, and self-healing ability for high-performance elastomers that can find applications such as skin-inspired wearable devices.