Tribological behavior and quantum chemical calculations of protic ionic liquids: synthesis, spectroscopic, and thermal properties

Abstract

Protic ionic liquids (PILs) were synthesized through a stoichiometric neutralization reaction between 2,2′-(ethylenedioxy)-bis(ethylamine) { Edbea} and various acids (formic, acetic, boric, decanoic, and gentisic acid). ThePILs were characterized by elemental analyses, FTIR, 1 H and 13 C NMR spectroscopy, and thermogravimetric analysis.All the PILs except PIL3 were liquid at room temperature. The viscosity of the PILs (PIL1, 2, 4, 5) was measuredusing a cone-and-plate viscometer at ambient temperature. Quantum chemical calculations were used to explain thecation/anion ratio in the PILs. Reaction energies in the gas phase calculated at M062X/6-311+G(d,p) level were used to determine the cation/anion ratio. A sliding wear test was conducted at room temperature using an AA7075 disc specimen against a stationary 100Cr6 steel ball. The wear protection of PILs and 15W40 engine oil was determined by considering the volume loss of AA7075.