Recoverable solvent-free small molecular supramolecular pseudoeutectic adhesives with a wide temperature range

Traditional petroleum-derived polymer adhesives can no longer meet the current demand for smart adhesion under harsh environmental conditions and sustainable development. The use of toxic solvents or volatile substances in these adhesives has raised significant environmental pollution concerns. Additionally, complex systems count against mechanism study. The structural prerequisites that govern self-assembly in gelators are always not well understood, even in the case of simple gelators. Therefore, there is an urgent need for the development of novel, simple, and solvent-free adhesive formulations suitable for harsh conditions. In this study, we explored a new type of pseudoeutectic hydroxyl-quaternary phosphate adhesive that can demonstrate robust bonding strengths (up to 2.14 MPa at −80 °C) across a broad temperature range (from −80 °C to 80 °C) on various surfaces (glass, steel, and PET). Moreover, this adhesive can be simply recycled from water and retains stable adhesion strength after several recovery cycles. The impact of structural modifications on adhesion was thoroughly investigated through molecular engineering. The results from molecular dynamics simulations corresponded closely to those from lap-shear experiments and shed light on the high interfacial energy observed on the iron surface. Notably, incorporating a small amount of ethylene glycol has been found to enhance durability significantly. An innovative solvent-free pseudoeutectic adhesive with hydroxyl phosphonium salt as monomers with excellent recyclability and robust adhesion across a broad temperature range is reported.