Dual dynamic epoxy vitrimer feasibly made from a bio-based hardener and PEG: Synthesis, physico-chemical properties, supramolecular effects, green chemistry metrics, and DFT study

In this study, we present the development of a novel epoxy vitrimer with dual reversible linkages. By integrating imine bonds within a vanillin-derived hardener structure and introducing supramolecular interactions through the addition of poly(ethylene glycol) (PEG), we have feasibly engineered a material exhibiting enhanced recyclability, reprocessability and healability. The presence of PEG induces supramolecular interactions particularly H-bonding, resulting in increased mechanical properties (e.g., fracture toughness from 0.844 to 1.019 MPa.m^0.5), thermal resistance, improved self-healing, higher storage modulus and faster stress relaxation. Our experimental findings, preliminarily verified by density functional theory (DFT) calculations, demonstrated an increase in interaction energy, confirming the synergistic effect of these dual reversible bonds. This dual bonding approach not only maintains the material's structural integrity and mechanical properties but also significantly improves its reprocessing and self-healing capabilities. Easy-to-use green chemistry metrics and simplified life-cycle assessment (LCA), i.e., EcoScale and GREEN MOTION scales, were also considered to provide an insight into the efficiency and greenness of the processes used to prepare the hardener and vitrimers. This work sets a precedent for future materials design, showcasing the potential of combining multiple dynamic bonding mechanisms to achieve superior material performance and sustainability.