Bioinspired Engineering of Two Different Types of Sacrificial Bonds into Chemically Cross-Linked <i>cis</i>-1,4-Polyisoprene toward a High-Performance Elastomer

The development of advanced elastomers with a combination of high strength, large extensibility, and excellent flex-cracking resistance is a huge challenge. In this contribution, we proposed a novel strategy to engineer a multinetwork by incorporating weaker sacrificial hydrogen bonds and stronger Zn-based units into a chemically cross-linked cis-1,4-polyisoprene network. The dynamic nature allows the sacrificial bonds to be ruptured and re-formed, resulting in high stretchability. During external loading, the sacrificial bonds rupture prior to fracture of the covalent network, thus dissipating energy efficiently and facilitating chain orientation to produce improved tensile modulus and fracture toughness as well as significant enhancement of flex-cracking resistance. We propose that the enhanced cracking resistance may originate from the energy dissipation and re-forming of sacrificial bonds, a new mechanism alternative to strain-induced crystallization. Overall, this concept provides unique inspiration for the design of advanced elastomers with excellent mechanical properties under both static and dynamic conditions.