High-Strength and Multi-Recyclable Epoxy Vitrimer Containing Dual-Dynamic Covalent Bonds Based on the Disulfide and Imine Bond Metathesis

Abstract

Epoxy (EP) vitrimers are currently regarded as ideal substitutes for traditional thermosetting resins, as this class of materials combines the advantages of thermoplastic and thermoset polymers. However, maintaining the high performance of EP vitrimers with excellent healing properties remains a challenge. In this work, a novel hardener combining disulfide and imine bonds through the reaction of Schiff base (4-AFD-VAN) was designed and then used to prepare the EP vitrimer with dual-dynamic covalent bonds. Compared to the single-disulfide-containing vitrimer (EVP-4-AFD), the prepared EP vitrimer (EPV-4-AFD-VAN) exhibited a lower activation energy and a faster stress relaxation. Moreover, EPV-4-AFD-VAN showed a tensile strength of up to 71.5 MPa and maintained a recovery ratio of approximately 90.0% during the three cycles. Similar to traditional thermoset EP, EPV-4-AFD-VAN retained its good solvent resistance, high breakdown strength, and good dielectric properties, which can be chemically degraded in suitable solvents, demonstrating its environmental sustainability.