Choline amino acid ionic Liquids: A novel green potential lubricant

Given the depletion of global energy and crisis of environmental pollution, the social demand for lubricants concerning green and socioeconomic benefits is becoming stronger. Herein, a series of eco-friendly, non-corrosive and cost-effective choline amino acid ionic liquids ([Ch][AA]) ILs were synthesized. Among the five [Ch][AA] ILs, long-alkyl-chain and guanidyl group-containing ILs display superior wettability, kinematic viscosity and load-carrying property. Regulation of tribological behavior is achieved through the assembly of anionic structure. Additionally, various friction conditions govern the lubrication regime of [Ch][AA] ILs. Concurrently, the friction-heat is predicted according to the thermal-physical properties. Furthermore, lubrication performance of [Ch][AA] ILs is comparable to polyalphaolefin oil (PAO 40) in various lubrication regime, which are attributed to the resulting thermal-physical properties and physical adsorption tribofilms. This work not only perfects the lubricating system of the [Ch][AA] ILs, but also is of great significance to elucidating the applicable conditions of desired [Ch][AA] ILs lubricants.