Non-ideal viscosity and excess molar volume of mixtures of 1-butyl-3-methylimidazolium tetrafluoroborate ([C4mim][BF4]) with water

Abstract

Densities and viscosities of binary mixtures containing 1-butyl-3-methylimidazolium tetrafluoroborate with water over the salt-rich region concentrations are reported for a temperature range of (283.15 to 373.15) K and compared with literature. The temperature dependence of the mixture densities and dynamic viscosities are accurately described by an empirical, linear relationship and by the Vogel-Fulcher-Tammann (VFT) equation, respectively. We identify a correlation between the excess mixture viscosity and the excess molar volume in the ionic liquid rich regime that is motivated by free volume theory. The broader validity of this correlation is tested against literature data for aqueous mixtures of similar ionic liquids.