Self-healing epoxidized natural rubber with ionic/coordination crosslinks

Self-healing polymers with strong mechanical robustness and superior self-healing ability are of interest in coatings, electronics, structural components, etc. However, it is difficult to realize these properties simultaneously, owing to the mutually exclusive requirements: the mechanical robustness of materials needs strong bonds to form robust network, but a strong bond leads to weak self-healing capability. In this work, we report the rational design of epoxidized natural rubber (ENR) incorporating with ionic and coordination supramolecular hybrid bond network, in which these two kinds of bonds possess identical cross-linking point yet contrasting bond strength. The optical microscope pictures and the temperature-dependent infrared spectra analysis show that ionic bonds rapidly shorten the spatial distance of the ENR chains located on both sides of the ionic bond to assemble into a stable network with lower energy state owing to its short temporal timescale for reconstruction, and simultaneously promote the reconstruction of coordination bond as a result of their sharing the same cross-linking point. The cooperative collaboration of these two bonds lead to a tensile stress of 1.33 MPa, a strain of 600%, and a healing efficiency of 92% after healing for 3 h at ambient temperature. This novel self-healing material is promising for various applications, especially when the component is difficult to disassemble or with limited enviroment conditions.