(636b) Electrolytic Conductivity, Density and Viscosity Measurements and Models for Ten Ionic Liquids

We were motivated to explore characteristic properties of ionic liquids with at least one benzylic substituent since they are representative segments of poly(ILs) and ionenes where imidazolium cations and benzylic groups are commonly found. Electrolytic conductivity measurements for a total of ten ionic liquids (ILs) (four N-alkyl-N-methyl pyrrolidinium cations [C_nmpyr] and six 1-(methyl)benzyl-3-alkyl imidazolium cations ([Bnmim] or [MeBnC_n mim]), all paired with bistriflimide [Tf₂N] anions) are reported at p = 0.1 MPa over T = (293.15 – 323.15) K. This work contributes electrolytic conductivity properties to our earlier report[1] of viscosity and density measurements. Prior to the study, our samples were thoroughly dried under vacuum and their water content before and after measurements was determined by Karl Fischer titration. For the conductivity measurements, an impedance bridge technique was used in conjunction with a sealed cell equipped with platinum black electrodes. The cell constant (K_cell = 101 m⁻¹) was determined with standard aqueous KCl solutions before and after measurements. The results show that electrolytic conductivity increases with increasing temperature in both families of ILs, while conductivity decreases as the length of the IL side chain increases, which is associated with increase in IL viscosity. Conductivities of the pyrrolidinium ILs were consistent with other data for these compounds already reported in the literature.[2] The conductivities of the 1-(methyl)benzyl-3-alkyl imidazolium ILs are shown to be reduced by (70-90) % compared to the analogous 1-alkyl-3-methylimidazolium ILs.
[1] Bara, J. E. Finotello, A., Magee, J. W., Qian, S., O’Harra, K. E., Dennis, G. P. and Noble, R. D., "110th Anniversary: Properties of Imidazolium-based Ionic Liquids Bearing both Benzylic and n- Alkyl Substituents,” Ind. Eng. Chem. Res. 58, 17956-17964 (2019) [DOI: 10.1021/acs.iecr.9b03159]
[2] Kazakov, A. F., Magee, J. W., Chirico, R. D., Diky, V., Kroenlein, K. G., Muzny, C. D. and Frenkel, M., "Ionic Liquids Database – ILThermo (v2.0)" NIST Standard Reference Database 147, National Institute of Standards and Technology Gaithersburg MD.