Discerning the Structure Factor of Charged Micelles in Water and Supercooled Solvent by Contrast Variation X-ray Scattering

Santosh L. Gawali, Mingming Zhang, Sugam Kumar, Debes Ray, Manidipa Basu, Vinod K. Aswal, Dganit Danino, Puthusserickal A. Hassan*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

3 Scopus citations

Abstract

Sodium dodecyl sulfate (SDS) is a well-known anionic surfactant that forms micelles in various solvents including supercooled sugar-urea melt. Here, we explore the application of contrast variation small-angle X-ray scattering (SAXS) in discerning the structure and interactions of SDS micelles in aqueous solution and in a roomerature supercooled solvent. The SAXS patterns can be analyzed in terms of a core-shell ellipsoid model. For aqueous SDS micelles, at low volume fractions, the features due to intermicellar interaction, S(q), in the SAXS pattern are poorly resolved because of the prominent contribution from shell scattering. Increasing the electron density of the solvent by the addition of the urea or fructose-urea mixture (at a weight ratio of 6:4) permits the systematic variation of shell scattering without influencing the structure drastically. For a 10% solution of SDS in water, the contribution from the shell can be completely masked by the addition of 40% urea or fructose-urea mixture. The fructose-urea mixture is a preferred additive as it can vary the scattering length density over a wide range and serves as a matrix to form supercooled micelles. The structural parameters of micelles in supercooled fructose-urea melt are obtained from contrast variation SAXS, small-angle neutron scattering, and high-resolution transmission electron microscopy.

Original languageEnglish
Pages (from-to)9867-9877
Number of pages11
JournalLangmuir
Volume35
Issue number30
DOIs
StatePublished - 30 Jul 2019
Externally publishedYes

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