Oleic Acid-Alcoholamine Protonated Ionic Liquid Lamellar Liquid Crystals: Enhancing Lubrication Properties and Corrosion Resistance

Lamellar liquid crystals (LLCs) exhibit significant potential in lubrication due to their unique layered structure. Introducing ionic liquids (ILs) to enhance the lubrication performance of the LLCs is a feasible approach. However, common ILs often demonstrate substantial corrosivity toward metals. In this study, LLCs were formed using oleic acid (OA) as the anion, alcoholamine solvents with corrosion-resistant properties (including monoethanolamine (MEA), diethanolamine (DEA), and triethanolamine (TEA)) as the cation, and glycerol (GL) as the solvent. The results reveal that the synergistic effect between the physical adsorption film and the tribochemical reaction film during friction significantly improves their lubricating performance. Notably, the OA/GL/MEA system outperforms OA/GL/DEA and OA/GL/TEA in lubrication properties, which can be attributed to its tighter intermolecular arrangement and smaller interlayer spacing, thereby providing enhanced mechanical strength. Furthermore, the ionic liquid-based LLCs exhibit negligible corrosiveness to steel, owing to the presence of carboxylic acid groups, unsaturated bonds, and hydroxyl groups in the molecular structure, which strengthen ILs adsorption on metal surfaces. Their combined lubrication efficacy and corrosion resistance render these LLCs highly promising for mechanical lubrication applications.