Dual-Dynamic Sacrificial Networks Enable Durable and Reprocessable Epoxidized Natural Rubber Elastomers

Conventional elastomer networks can provide mechanical stability but offer limited capacity for network rearrangement and reprocessing. In this work, a sulfur-rich oligomeric crosslinker (S-VBGE) was introduced into epoxidized natural rubber (ENR) to construct a filler-free dual-dynamic network containing reversible hydrogen-bonding associations and sulfur-containing dynamic structures. The optimized ENR-SV15 formulation reached a tensile strength of 14.84 MPa and a toughness of 85.07 MJ·m−3. Based on three independent fatigue crack growth measurements, its apparent fatigue threshold was 310 ± 14 J·m−2, compared with 41 ± 1 J·m−2 for ENR-0. Temperature-dependent stress relaxation and reprocessing experiments indicate thermally activated network rearrangement, while variable-temperature FTIR supports the thermal responsiveness of the hydrogen-bonding associations. Together, these results show that balancing reversible associations, sulfur-containing dynamic structures, and network constraints can improve crack growth resistance while retaining solid-state reprocessability in dry ENR elastomers.