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.
