Robust lubricity and multifunctional water-based lubrication system induced by ionic liquids with its interfacial self-assembly behavior and unique hydration structure

Efficient lubrication at low concentration has always been the pursuit of mechanical equipment in engineering applications, and breakthroughs for high performance are urgently needed, as well as the consideration of cost and sustainability. Therefore, water-based lubricants have become a crucial and potential lubricating system. Herein, a novel ionic liquid (IL) water-based lubrication system was constructed, achieving superior lubricity and long-term stability, whose optimal anti-friction performance and corrosion resistance are reduced by more than 80 %. More importantly, its versatility (anti-corrosion, strong adsorption, anti-wear and load-bearing) is also essential. Of course, these improved performances are inseparable from the multiple interactions (hydrogen bond, competitive adsorption, electrostatic interaction, tribo-chemistry) between ILs and engineering metal surfaces. More interestingly, the exploration of interaction mechanism inspires more in-depth insights for self-assembly behavior for IL aqueous system at the metal interface. From in-depth insights on lubricating mechanism, the hydration shell induced by polar groups and interfacial tribochemical reaction are predominant in competitive adsorption, which can be inferred from the molecular dynamics simulation data. As far as the interaction force is concerned, the struggle and balance among adsorption energy, hydrogen bond and electrostatic interaction force reveal the synergistic lubrication mechanism of multiple interaction force coupling. Besides, the structure–activity relationship between system composition and performance provides theoretical guidance for its practical engineering application, which also can be expanded as an important theoretical basis and experimental references for aqueous lubrication.