Inverse Vulcanized Polysulfide-Mediated Efficient Crosslinking of Epoxy Elastomers: Mechanism and Recyclability

Abstract

Incorporating dynamic covalent bonds into epoxy thermosets offers a promising route to confer recyclability, yet the development of efficient and scalable strategies for constructing dynamic epoxy networks remains challenging. Herein, an inverse vulcanized polysulfide (SP), synthesized from elemental sulfur and styrene, was directly employed as a crosslinker and a dynamic S–S bond reservoir for an epoxy-based elastomer ethylene-vinyl acetate-glycidyl methacrylate terpolymer. The polysulfide bonds in SP are subjected to heterolytic cleavage via nucleophilic activation by 1,2-dimethylimidazole, producing thiolate species that subsequently couple with epoxy groups, thereby constructing a crosslinked network comprising dynamic disulfide and polysulfide motifs. The crosslinking mechanism was verified by model reactions and density functional theory calculations. Moreover, the crosslinking density and network structure of the resulting elastomers can be regulated by varying the SP content, leading to tunable thermomechanical properties and dynamic behaviors. Additionally, dynamic S–S metathesis endows the crosslinked elastomer with topological rearrangement, thereby conferring reprocessability. The recycled elastomer retains a high recovery efficiency of mechanical properties. This work provides a facile and sustainable strategy for constructing recyclable epoxy elastomers and expands the application potential of inverse vulcanized polysulfides in dynamic epoxy thermosets.