Surface tension and 0.1 MPa densities of imidazolium-, pyridinium-, pyrrolidinium-, and piperidinium-based tris(pentafluoroethyl)trifluorophosphate ionic liquids

Abstract

Experimental data over the temperature range from 263 to 363K are presented on the air–liquid interfacial tension and 0.1MPa densities for four ionic liquids with the tris(pentafluoroethyl)trifluorophosphate (FAP) anion and with the 1-(2-methoxyethyl)-1-methylpyrrolidinium, 1-(2-methoxyethyl)-1-methylpiperidinium, N-(3-hydroxypropyl)pyridinium, and 1-(2-hydroxyethyl)-3-methylimidazolium cations. The surface tension data were obtained by the Wilhelmy plate method with an estimated combined expanded uncertainty at 0.95 confidence level of ±0.2mNm−1. The reported density data were obtained using a single-sinker buoyancy method with an estimated expanded combined uncertainty at 0.95 confidence level ±0.8kgm−3 (4.6×10−4ϱ). The Krűss K100MK2 tensiometer was used to determine the surface tension and buoyancy forces. A value of 224.79cm3mol−1 follows for the FAP anion contribution to the ionic liquids molar volume at 298.15K and 0.1MPa from the group contribution analysis of the density data. In contrast to the common organic liquids, the studied ionic liquids show a negative value of the temperature derivative of the isochoric thermal volume expansion coefficient in the studied temperature interval.