Viscosity of (C2-C14) 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide ionic liquids in an extended temperature range

Dynamic viscosities of several members of the 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide, [C_nmim][NTf₂], ionic liquids family, with the cation alkyl side-chain length varying from 2 to 14 carbon atoms, have been measured in the 278.15 K to 393.15 K temperature range using two different apparatuses. To the best of our knowledge, it is the first time that such an extensive assessment of viscosity - in terms of the number of compounds of a single ionic liquid homologous series, of the broad range of temperature covered, and the use of two different experimental techniques - is reported. The use of two different instruments, using different methodologies, provides information about the uncertainties in the measurement of viscosity of ionic liquids, including its dependence on the presence of traces of water and other impurities. An extensive critical analysis of the deviations between the data measured in this work and those reported in literature has been carried out.