High accuracy NMR chemical shift corrected for bulk magnetization as a tool for structural elucidation of microemulsions. Part 2 - Anionic and nonionic dilutable microemulsions

Roy E. Hoffman*, Eliezer Darmon, Abraham Aserin, Nissim Garti

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

5 Scopus citations

Abstract

In our previous report we suggested a new analytical tool, high accuracy NMR chemical shift corrected for bulk magnetization as a supplementary tool to study structural transitions and droplet size and shape of dilutable microemulsions. The aim of this study was to show the generality of this technique and to demonstrate that in almost any type of microemulsion this technique provides additional valuable structural information. The analysis made by the technique adds to the elucidation of some structural aspects that could not be clearly determined by other classical techniques.Therefore, in this part we are extending the study to three additional systems differing in the type of oil phase (toluene and cyclohexane), the nature of the surfactants (anionic and nonionic), and other microemulsion characteristics.We studied sodium dodecyl sulfate (SDS)-based anionic microemulsions with different oils and a nonionic microemulsion based on Tween 20 as the surfactant and toluene as the oil phase. All the microemulsions were fully dilutable with water.We found that the change in the slope of chemical shift against dilution reflects phase transition points of the microemulsion (O/W, bicontinuous, W/O). Chemical shift changes were clearly observed with the transition between spherical and non-spherical (wormlike, etc.) droplet shapes. We compared the interaction of cyclohexane and toluene and used the anisotropic effect of toluene's ring current to determine its preferred orientation relative to SDS.Chemical shifts of the microemulsion components are therefore a useful addition to the arsenal of techniques for characterizing microemulsions.

Original languageEnglish
Pages (from-to)358-366
Number of pages9
JournalJournal of Colloid and Interface Science
Volume463
DOIs
StatePublished - 1 Feb 2016

Bibliographical note

Publisher Copyright:
© 2014 Elsevier Inc.

Keywords

  • Chemical shift
  • Microemulsion
  • U-type microemulsion

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