One-Pot Solvent-Free\nSynthesis of Imine-Based Epoxidized\nSoybean Oil Vitrimers for Sustainable Adhesives

The traditional methods for synthesizing imine-based\nepoxidized\nsoybean oil (ESO) vitrimers often rely on organic solvents, leading\nto issues such as incomplete raw material conversion, increased production\ncosts, and environmental concerns, contradicting the principles of\ngreen and sustainable chemistry. To overcome these challenges, we\npropose an innovative one-pot, solvent-free approach for synthesizing\nimine-linked ESO vitrimers via a melt reaction utilizing ESO, vanillin,\nand diamines. In this system, three distinct reactions can occur:\nphenolic hydroxy-epoxy, amino-aldehyde, and amino-epoxy. Our findings\nindicate that the first two reactions occur more readily and rapidly\nthan the third, facilitating the successful synthesis of the vitrimers.\nWe employed three different diamines to tailor the chemical structure\nand control properties of the ESO vitrimers; aromatic diamines produced\nrigid vitrimers with high strength but low ductility, while aliphatic\ndiamines yielded flexible vitrimers with lower strength but higher\nductility. All vitrimers exhibited rapid high-temperature stress relaxation\nand excellent reprocessability and thermal stability. Notably, these\nvitrimers demonstrated impressive adhesive properties, achieving lap\nshear strengths between 4.0 and 6.7 MPa when applied to various substrates,\nincluding wood, steel, and aluminum. Moreover, the dynamic imine bonds\nenable exceptional recyclability, removability, and reusability, with\nrecycled ESO vitrimers even surpassing their virgin counterparts in\nmechanical and adhesive performance, underscoring the significance\nof this work in advancing sustainable adhesive materials with enhanced\nfunctionality and circularity.