Dynamic co‐ordination networks in carboxylated nitrile rubber and development of self‐healing and recyclable rubber composites

Abstract Metal–ligand coordinated cross‐linked polymeric composites that can alter the network topology via a dynamic bond‐exchange mechanism have been recognized as very promising candidates to address the shortcomings of conventional cross‐linked composites, such as poor recyclability and self‐healing ability. This has led to much interest in the cross‐linking of elastomers via non‐covalent interactions with suitable metal ions. In this report, we present a simple but efficient approach to ferric ions (Fe 3+ ) assisted crosslinking of carboxylated nitrile rubber (XNBR) in the presence of an aliphatic amine (Et 3 N). The dynamic coordination reaction via carboxylate functional group of nitrile rubber (XNBR) is employed to fulfill the coordination requirements of the central Fe 3+ metal ion. This is confirmed by x‐ray photoelectron spectroscopy and Fourier‐transform infrared spectroscopy. The crucial role of Et 3 N in partially hindering and regulating the extent of crosslinking is investigated and mechanistically interpreted by swelling, differential scanning calorimetry, and rheological study. The tensile strength of ferric crosslinked XNBR could be enhanced up to four times than that of pure XNBR. Furthermore, the dynamic coordination‐driven network of XNBR offers excellent self‐healing (90% efficiency) and recyclability features (80% efficiency) for a composite of appropriate formulations.