Deviations from ideality in mixtures of two ionic liquids containing a common ion

José N. Canongia Lopes, Telma C. Cordeiro, José M. S. S. Esperança, Henrique J. R. Guedes, Susanne Huq, Luis P. N. Rebelo, Kenneth R. Seddon

Research output: Contribution to journalArticlepeer-review

66 Citations (Scopus)


Excess molar volumes of six binary mixtures composed of two ionic liquids of the 1-methyl-3-alkylimidazolium bis(trifluoromethylsulfonyl)amide family-([Cmmim] + [Cnmim])[NTf2] with n and m ranging from 2 to 10 - were measured for several compositions at 298 and 333 K. Similarly, three other binary systems containing [C4mim]+ (1-methyl-3-butylimidazolium) as a common cation have been studied: [C 4mim]([NTf2] + [PF6]), [C4mim] ([NTf2] + [BF4]) and [C4mim]([BF4] + [PF6]). Thus, the mixing process of two distinct ions of equal sign embedded in a constant field network of a given counterion was analyzed. All systems exhibit small, positive VE values of the order of a few tenths of cm3 mol-1, which are essentially temperature and pressure independent. The results show additive trends, for instance, the VE values become larger as the difference between the alkyl chain lengths of the two cations increases. The Flory theory of mixtures provides a useful, semiquantitative correlation between the excess volumes and excess enthalpies in these systems, allowing for comparison with analogous results obtained within the linear primary alcohols.

Original languageEnglish
Pages (from-to)3519-3525
Number of pages7
JournalJournal of Physical Chemistry B
Issue number8
Publication statusPublished - 3 Mar 2005


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