Task–specific Ionic Liquids Based on Sulfur for Tribological Applications

Ionic liquids (ILs) have been recently considered as potentially adequate lubricants for microelectromechanical and nanoelectromechanical systems ( MEMS/NEMS) due to the specific features of these silicon based miniaturized devices. Aiming at the optimization of the lubrication of MEMS/NEMS, new ILs resulting from the combination of sulfur‐containing anions (bis(2‐ethyl‐1‐hexyl) sulfosuccinate, [AOT], and ethylsulphate, [C 2 SO 4 ]) with ammonium, imidazolium or methylpyridinium based cations were prepared. Their tribological performance against silicon and steel was assessed with a nanotribometer and compared to that of other ILs based on the cation 1‐ethyl 3‐methylimidazolium, [C 2 MIM]. Our results reveal that the presence of the anion [C 2 SO 4 ] is responsible for very low friction coefficients on silicon, meaning that these ILs may be considered as promising lubricants for MEMS/ NEMS. In contrast, the anion [AOT] did not lead to efficient lubricants for this type of systems. The results obtained on steel were not so impressive, although all the ILs based on [C 2 SO 4 ] presented better lubricant capacities than commercial oil.