Ionic Liquid Tunes Microemulsion Curvature

Julian G Eastoe

Research output: Contribution to journalArticle (Academic Journal)peer-review

46 Citations (Scopus)

Abstract

Middle-phase microemulsions formed from cationic dioctadecyldimethylammonium chloride (DODMAC), anionic
sodium dodecylsulfate (SDS), n-butanol, and n-heptane were studied. An ionic liquid (IL), 1-butyl-3-methylimidazolium
tetrafluoroborate ([bmim][BF4]), was employed as the electrolyte in the aqueous media instead of inorganic salts
usually used in microemulsion formulation. Studies have been carried out as a function of the concentrations of
[bmim][BF4], n-butanol, total surfactant (cDODMAC+SDS), and temperature on the phase behavior and the ultralow
interfacial tensions in which the anionic component is present in excess in the catanionic film. Ultralow interfacial
tension measurements confirmed the formation of middle-phase microemulsions and the necessary conditions for
stabilizing middle-phase microemulsions. Electrical conductivity, small-angle X-ray scattering (SAXS), and smallangle
neutron scattering (SANS) experiments were also performed, indicating that the typical heptane domain size
has an average radius of 360 Å and the ionic liquid induces softening of the charged catanionic film. Most interestingly,
the IL concentration (cIL) is shown to act as an effective interfacial curvature-control parameter, representing a new
approach to tuning the formulation of microemulsions and emulsions. The results expand the potential uses of ILs
but also point to the design of new ILs that may achieve superefficient control over interfacial and self-assembly
systems
Original languageEnglish
Pages (from-to)2055-2059
Number of pages7
JournalLangmuir
Volume25
DOIs
Publication statusPublished - 2009

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