Effects of alkyl chain on transport properties in 1-alkyl-3-methylimidazolium hexafluorophosphates

We studied the transport properties in a series of 1-alkyl-3-methylimidazolium hexafluorophosphates with the alkyl side chains being butyl, hexyl, and octyl, which are expressed by [BMIM][PF6], [HMIM][PF6], and [OMIM][PF6], respectively. The self-diffusion coefficients of the cation (Dcation) and anion (Danion) species in the ionic liquids were independently determined at a fixed temperature of 323.2±0.1 K by observing 1H and 19F nuclei with the pulsed-field gradient spin-echo NMR technique together with the electric conductivities. Based on these experimental results, the effects of alkyl side chain on transport properties in 1-alkyl-3-methylimidazolium hexafluorophosphates were discussed in terms of interionic interactions.