Enhanced design of dual dynamic cross-linked rubber composites: Achieving self-healing and recyclability through imine and metal-ligand bonding

The quest to confer self-healing and recyclable properties to conventional rubber is a prominent research area in the rubber industry. This study presents the novel construction of a self-healing and recyclable rubber composite by employing imine bond and Cu2+-imine cross-linking the polybutadiene rubber matrix and Cu2+-imidazole groups cross-linking at the silica-rubber interface. The introduction of imine bonded cross-linked imparts high elasticity to the rubber, while the Cu2+-imidazole complex serves as a bridge, enhancing the interfacial interaction between the silica and rubber matrix. The Cu2+-N (Cu2+-imidazole and Cu2+-imine) complexes not only improves silica dispersion but also acts as a sacrificial unit, thereby enhancing the mechanical properties of the rubber composites. The addition of 0.2 mmol anhydrous copper (II) chloride (CuCl2) results in a significant increase in tensile strength and Young's modulus of the samples (1.04 and 3.91 MPa), with improvements of 181 % and 407 %, respectively, compared to the pure samples. Additionally, the highly dynamic nature of the imine bond and the Cu2+-N (Cu2+-imidazole and Cu2+-imine) complexes imparts excellent self-healing and recyclable properties to the material, exhibiting repair efficiency and recycling recovery of up to 90 % (tensile strength). Therefore, this work opens a new avenue for the design and development of self-healing, recyclable rubber composites.