Bioinspired Engineering of Sacrificial Metal-Ligand Bonds into Elastomers with Supramechanical Performance and Adaptive Recovery

Reinforcing rubbers and expanding their application galleries are two important issues in material science and engineering. In this work, we demonstrate a bioinspired design of high-performance and macroscopically responsive diene-rubber by engineering sacrificial metal-ligand motifs into a chemically cross-linked architecture network. The metal-ligand bonds are formed through the coordination reaction between the pyridine groups in butadiene-styrene-vinylpyridine rubber (VPR) and metal ions. Under external load, the metal-ligand bonds serve as sacrificial bonds that preferentially rupture prior to the covalent network, which dissipates energy and facilitates rubber chain orientation. Based on the function mechanisms, the modulus, tensile strength, and toughness of the samples are simultaneously improved without sacrificing the extensibility, and these properties can be conveniently tuned by varying the structure parameters of the covalently cross-linked network and metal-ligand bonds. Moreover, the dissociation/re-formation of metal-ligand bonds upon heating/cooling can endow VPR with thermally triggered adaptive recovery for shape memory application.