Abstract
Methylation of the C(2) carbon on imidazolium-based room temperature ionic liquids (RTILs) causes an unexpected increase in viscosity when paired with the anion bis(trifluoromethylsulfonamide) [Tf2N]−, but the viscosity decreases when the methylated imidazolium is paired with a tetracyanoborate [B(CN)4]− anion. This paper investigates these different observations in viscosity using the compensated Arrhenius
formalism (CAF) for fluidity (inverse viscosity), which assumes fluidity to be a thermally activated process. CAF activation energies are determined for imidazolium [Tf2N]− and methylated imidazolium [Tf2N]− and compared to imidazolium [B(CN)4]− and methylated imidazolium [B(CN)4]−. The results show that the activation energy increases with methylation for [Tf2N]−, but it decreases with methylation for [B(CN)4]−. The CAF results also yield information concerning the entropy of activation, which are compared for the two systems
