Effects of dynamic crosslinking and static crosslinking on the mechanical properties of dual-crosslinked elastomers

Elastomers with high mechanical performance are indispensable in engineering applications, although traditional covalent crosslinking faces an inherent trade-off between stretchability and stiffness. The introduction of dynamic crosslinks in addition to covalent (static) crosslinks, i.e., the dual-crosslinking strategy, has been explored as a promising way to overcome this trade-off. However, the optimal balance between dynamic and static crosslinking remains unclear. In this study, we systematically investigated the effects of static and dynamic crosslinking on the mechanical properties of dual-crosslinked elastomers based on styrene–butadiene rubber (SBR). The metal‒ligand coordination of the pyridine-functionalized SBR with Zn 2+ ions served as dynamic crosslinks, and static crosslinks were induced through simple thermal treatments. The contents of dynamic crosslinks and static crosslinks were systematically varied, and various mechanical properties, such as tensile properties, strain rate–dependent tensile properties, energy dissipation efficiency, and recoverability, were examined. Increasing the dynamic crosslink density effectively increased the stiffness without sacrificing stretchability because of efficient energy dissipation. The dynamic crosslinks were also superior to the static crosslinks in terms of fatigue recoverability. These findings offer a promising strategy for designing high-performance elastomers with tailored mechanical properties.