Miscibility and distribution of counterions of imidazolium ionic liquid mixtures at the air/water surface

Kei Shimamoto, Asuka Onohara, Hiroki Takumi, Iwao Watanabe, Hajime Tanida, Hiroki Matsubara, Takanori Takiue, Makoto Aratono

Research output: Contribution to journalArticlepeer-review

14 Citations (Scopus)

Abstract

The miscibility and distribution of Br- and BF4 - ions of imidazolium ionic liquid mixtures, l-hexyl-3- methylimidazolium bromide (HMIMBr) + l-hexyl-3-methylimidazolium tetrafluoroborate (HMIMBF4), at the air/water surface were investigated by surface tensiometry and the total-reflection XAFS (TRXAFS) method. Tensiometry showed that the surface density Of BF4 - was much larger than that of Br-, the adsorbed films of the HMIMBr-HMIMBF4 mixture were greatly enriched in BF 4- at all surface tensions, and the excess Gibbs energy of adsorption was positive. However, TRXAFS revealed that the Br ions were all in the free-Br state solvated by six water molecules in the mixed adsorbed film. Entropy-originated nonideal mixing, where a kind of segregation of the counterion distribution takes place in the interfacial region, was suggested in the mixture.

Original languageEnglish
Pages (from-to)9954-9959
Number of pages6
JournalLangmuir
Volume25
Issue number17
DOIs
Publication statusPublished - Sep 1 2009

All Science Journal Classification (ASJC) codes

  • Materials Science(all)
  • Condensed Matter Physics
  • Surfaces and Interfaces
  • Spectroscopy
  • Electrochemistry

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