Physical Properties of Selected Ionic Liquids for Use as Electrolytes and Other Industrial Applications

The physical properties of selected room temperature ionic liquids (RTILs) were measured using differential scanning calorimetry, du Nouy tensiometry, and rheometry primarily to determine their suitability for use in electrochemical double layer capacitors. RTILs have other uses, however, such as liquid-liquid extraction, catalysis, and heat transfer, and these measurements may also be of use to researchers working in other fields. The ionic liquids used were 1-ethyl-3-methylimidazolium dicyanamide [emim][N(CN)(2)], 1,2-dimethyl-3-propylimidazolium bis(trifluoromethylsulfonyl)imide [dmpim] [Tf(2)N], and 1-butyl-1-methylpyrrolidinium tris(pentafluoroethyl)trifluorophosphate [bmpyr][Pf(3)PF(3)]. Glass transition temperatures, crystallization and melting temperatures, surface tensions, and viscosities are reported. The three ionic liquids displayed a range of crystallization behaviors when cooled to 123.15 K and reheated to 403.15 K. All liquids were Newtonian over a range of shear rates from (10 to 1000) s(-1). Viscosities decreased with temperature, and this has been modeled using the Williams-Landel-Ferry equation.