Design of ionic liquids (ILs) with low viscosity/high diffusivity is extremely desirable for applications of ILs. Two different approaches are generally used: different combinations of cation and anion species, and modifications of alkyl chain lengths/functional groups of mainly cationic species. Here we report on computer simulation study of ion diffusivity in a series of ILs based on modified choline cations of differing chain lengths, paired with bis(trifluoromethylsulfonyl)imide (Tf2N) anions. The cations considered are N,N,N-trimethylethanolammonium ((CH3)3N(CH2)2OH) modified by replacing one of its methyl groups with an alkylamine group �(CH2)mNH2 (2 = m = 20). Interestingly, it is found that m = 5 yields the highest ion diffusivity. For m < 5, the ion diffusion coefficients increase with m, while the opposite trend is obtained for m > 5. Our study thus shows that an increase in the cation alkyl chain length does not necessarily lead to a decrease in ion diffusivity, at least for the choline-based ILs we investigated. This finding could be useful in the design of novel low viscosity ionic liquids.

Computational study of diffusive behavior of choline-based ILs

248th National Meeting (2014)

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