Poly(ionic liquid)s with amino acids counterions as multifunctional water-based additives contributing to green lubrication

Three halogen-free poly(ionic liquid)s (PILs), composed of polycations (poly(PEGMA-co-METAC), PPM) and different amino acid anions as counterions, were synthesized. The physicochemical properties of three PILs were characterized to confirm their efficacy as viscosity-enhancing additives. The tribological properties of aqueous lubricants containing PILs were investigated by the SRV-IV test. The addition of three PILs to water resulted in remarkable improvements in kinematic viscosity, lubricity, and anti-wear properties. Among them, PPM-Try demonstrated the best tribological performance due to the formation of the more superior protective film on the friction interface through a tribochemical reaction. Furthermore, PPM-Try is non-toxic to environment and demonstrates favorable antibacterial properties, rendering it a promising eco-friendly aqueous lubricant additive for applications in the metalworking and food industry.