Mechanically robust, super tough and ultrastretchable self-healing polyurethane constructed from multiple asymmetric hydrogen bonds

Self-healing materials with adjustable mechanical properties and customizable chemical structures have garnered significant attention due to their rapid healing rates and high healing efficiencies, especially those with multiple hydrogen bond structures. In this work, 2,5-dithiobiurea was innovatively introduced to successfully synthesize a self-healing polyurethane (IE-PU) dominated by multiple asymmetric hydrogen bonds. The incorporation of dithiourea structure promotes the formation of multiple asymmetric hydrogen bonds between molecular chains, significantly reducing the crystallinity of the material while maintaining the flexible mobility of the chain segments, allowing for rapid recovery of damaged areas. The prepared IE-PU exhibits excellent tensile strength ($\sim$ 36 MPa), robust toughness ($\sim$ 220 MJ/m³), an ultra-high elongation at break ($\sim$ 1600 %), and a high healing efficiency ($\sim$ 95 %). Furthermore, a conductive composite film was prepared by surface compounding of IE-PU and carbon black. The composite film maintains good electrical conductivity after bending, stretching, and fracture healing. The results indicate that the conductivity of the composite film remains unaffected by these operations. Therefore, the prepared PU not only demonstrates exceptional performance but also holds broad application prospects, such as in coatings, flexible substrates, and films, showcasing its potential value across multiple fields.