Constructing Fully Biobased Epoxy Vitrimer Based on Disulfide Bonds with Desired Mechanical, Recyclability, and Degradability Properties

Abstract

The development of biobased epoxy vitrimer materials aligns with environmental sustainability. However, constructing fully biobased dynamic cross-linking networks that integrate mechanical, reprocessability, and degradability remains a significant challenge. In this work, a fully biobased epoxy vitrimer with a disulfide bond-decorated dynamic covalent network was developed using biomass-derived diphenolic acid and cystamine. Diphenolic acid underwent an amidation reaction with cystamine, followed by epoxidation to form an epoxy monomer, which was further cured with cystamine to obtain fully biobased epoxy vitrimers. The as-prepared epoxy vitrimers exhibited excellent mechanical properties and thermal stability, attributed to the high cross-linking density and topological interlocking structure induced by amidation. The dynamic cross-linking network endowed the epoxy vitrimers with good self-healing and reprocessability through disulfide bond exchange reactions, while the disulfide bonds could enable degradability when treated with dithiothreitol. When epoxy vitrimers were used as a matrix to form carbon fiber-reinforced composites, the obtained composites exhibited a tensile strength exceeding 613.53 MPa. The resin matrix could be completely degraded in 2.5 h without compromising the structure or properties of the carbon fibers. This work offers insights into the design of fully biobased epoxy vitrimers and their carbon fiber composites.