(531d) Effect of Surface Chemistry on Tribological Behavior and Molecular Structuring of Nanoconfined Ionic Liquids

Ionic liquids (ILs) are known to exhibit unique properties such as low volatility, wide liquid temperature window, extraordinary chemical and thermal stability, all of which evoke extensive interests for a wide range of constructive applications including active lubrication. Nevertheless, in the past decade, the feasibility of utilizing ILs as lubricant additives has been well explored, the near-surface lubricated performance of ILs has not been specifically evaluated under given degrees of confinement in conjunction with molecular structuring affected by the close proximity of surfaces. Surface Force Apparatus (SFA) is utilized to investigate film structure and molecular orientation of 1-methyl-3-octylimidazolium tetrafluoroborate ([OMIM]⁺[BF₄]^-, C8) confined between hydrophilic and hydrophobic surfaces. On account of surface chemistry, C8 exhibits distinguishable film structures while confined between two hydrophilic or hydrophobic surfaces at a separation distance of serval nanometers, which results in distinct frictional behaviors in the vicinity of surfaces. Kinetic tribological behaviors of C8 under various normal pressure and sliding velocity are quantified at different film structures with contractive surfaces. We anticipate our findings would contribute impact of nature of confining surface on ILs structuring and performance which provides fundamental insights into wear protection mechanism as well as crucial operation parameters for industrial applications such as micro-/nano-electromechanical systems.