Enhancing mechanical properties and stabilising the structure of epoxide natural rubber using non-covalent interactions: Metal-ligand coordination and hydrogen bonding

Non-covalent interactions can enhance the mechanical properties of rubber materials diversifying potential applications. Epoxidized natural rubber (ENR), derived by modifying natural rubber (NR), can establish metal-ligand (M-L) coordination and H-bonding. In this research, ENR samples with non-covalent interactions were prepared by adding (i) sodium alginate (Alg) with FeCl3 and (ii) dopamine (D) with FeCl3. Both H-bonding and M-L coordination were detected by FTIR and Raman spectroscopy. The overall mechanical properties were increased due to non-covalent interactions, especially self-healing performance, which reached 60 %. From the mechanical stability data, storage hardening phenomenon of ENR was explained for the first time. These samples exhibited constant Mooney viscosity as a function of time. Furthermore, the effect of M-L coordination in dopamine modified samples were the strongest due to dopamine was grafted on ENR molecules. Therefore, this research provides a possible new way to stabilise the structure and enhance the mechanical properties of ENRs.