Polyethylene glycol functionalized dicationic ionic liquids with alkyl or polyfluoroalkyl substituents as high temperature lubricants

Abstract

A series of new polyethylene glycol functionalized dicationic ionic liquids with alkyl or polyfluoroalkyl substitutents (9–17 and 19–24) has been prepared. Important physical properties of these liquids, including glass transition (T_g) and decomposition temperatures (T_d), solubility in common solvents, density (d) and viscosity (η), were measured. These ionic liquids show high thermal stability and good lubricity. In general, imidazolium based dicationic liquids have higher T_d (>415 °C) than their triazolium analogues. The introduction of polyfluoroalkyl groups boosts antiwear properties but also leads to a decrease in T_d. These ionic liquids also exhibit excellent tribological characteristics even at 300 °C, which suggests use as high temperature lubricants.