A Biobased Epoxy Vitrimer with Dual Relaxation Mechanism: A Promising Material for Renewable, Reusable, and Recyclable Adhesives and Composites

This study presents the synthesis of a novel biobased epoxy monomer derived from vanillin and cystamine, incorporating imine and disulfide exchangeable groups within its structure. A series of epoxy-based vitrimers with two simultaneous exchange relaxation processes have been produced using this monomer. These exchange mechanisms operate without the need for any catalyst. Four different amine curing agents have been employed to achieve vitrimers with glass transition temperatures around 100 °C and excellent thermal stability. Through dynamic-mechanical analyses, thermomechanical properties and vitrimeric characteristics have been investigated, revealing remarkably fast stress relaxation at relatively low temperatures without significant creep below the glass transition temperature. Leveraging the dual exchange mechanism, the chemical degradability of these vitrimers has been explored through two accessible methodologies, and the material's reformation after degradation has been demonstrated in both cases. Furthermore, the material has been mechanically recycled, maintaining almost the same properties. Finally, these materials have been used to fabricate and recycle carbon-fiber-reinforced composite material and reversible adhesives, showcasing their promising potential applications.