Design and fabrication of mechanically strong and self-healing rubbers via metal-ligand coordination bonds as dynamic crosslinks

Developing mechanically strong and efficient self-healing rubbers is booming and shows great potential in a wide range of applications. Herein, by introducing pyridine ligands onto rubber chains via ring-opening reaction between epoxy groups and aminopyridine, we constructed dynamic Fe3+-pyridine coordination bonds in commercially available epoxidized natural rubber (ENR). The reversible nature of the coordination bonds endows the rubbers with efficient self-healing behavior under moderate conditions. Meanwhile, the coordination bonds can also serve as crosslinking points, which enhanced mechanical properties of the fabricated rubbers. When the molar ratio of Fe3+ to pyridine was 1 : 4, the tensile strength and 100% modulus reached 2.23 and 0.78 MPa, which are 18-times and 8-times that of the neat sample. Noteworthy, the sample also shows excellent self-healing capability with healing efficiency of 87% (tensile strength). Furthermore, by embedding conductive materials, we designed a conductive rubber with sandwich structure, which exhibits sensitive strain sensing behavior in detecting small strains.