Tough, self-healing, and recyclable cross-linked polyurethane elastomers via synergistic effect of dual dynamic covalent bonds

Based on the irresistible inherent trade-off between the mechanical and self-healing performances of cross-linked polyurethane materials, there is still an intractable challenge to design efficient self-healing and tough elastomers, especially in flexible sensors. Herein, a tough, efficient self-healing, and recyclable cross-linked polyurethane elastomer (DTPU) was prepared by integrating oxime-carbamate bonds and thiourethane bonds into the network. The extraordinary mechanical properties and self-healing performances of DTPU elastomers were related to the synergistic effect of oxime-carbamate bonds in the main chain and thiourethane bonds in the chemical cross-linked sites. The existence of dynamic cross-linked points not only optimized the mechanical properties of DTPU but also provided support for the reversible cleavage and formation of oxime carbamate bond, thus endowing DTPU with efficient self-healing performance and recyclability. After self-healing at mild temperatures for 6 h, the self-healed DTPU elastomers had a tensile strength of 30.27 MPa and a self-healing efficiency of 95.5%. After multiple hot-pressing, the original mechanical strength of DTPU was restored to over 100%, exhibiting excellent recyclable characteristics. Additionally, strain sensors based on self-healing flexible elastomers were fabricated by introducing conductive carbon nanotubes. The strain sensors maintained their electrical conductivity after 3 times self-healing, demonstrating great potential in healable flexible electronics.