Action of hydrotropes in water-in-CO2 microemulsions

Ci Yan, Masanobu Sagisaka, Craig James, Sarah E. Rogers, Jocelyn Peach, Marios Hopkins Hatzopoulos, Julian Eastoe*

*Corresponding author for this work

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

13 Citations (Scopus)
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The effects of a homologous series of sodium p-n-alkylbenzoate hydrotropes in water-in-supercritical CO2 (w/c) microemulsions have been investigated, by comparing the phase behaviour and droplet structures obtained using small-angle neutron scattering (SANS). The w/c microemulsions appeared to be generally stable upon addition of hydrotropes, however, on increasing the alkyl chain length of the hydrocarbon and fluorocarbon moieties of the surfactants, different effects on stability were observed. Using high-pressure SANS (HP-SANS), the effects of hydrotrope type on the structures of microemulsion droplets were studied. Interestingly, evidence was found for multiple shell structures with a hydrotrope rich layer between the water cores and the surfactant films. These findings are relevant to the understanding of self-assembly of co-adsorbed species in supercritical CO2 (scCO2), as the hydrotrope layers potentially have significant effects on surfactant packing, and can modify the physico-chemical properties of scCO2 through formation of worm-like micellar assemblies.

Original languageEnglish
Pages (from-to)76-82
Number of pages7
JournalColloids and Surfaces A. Physicochemical and Engineering Aspects
Early online date24 Mar 2015
Publication statusPublished - 5 Jul 2015


  • Fluorinated surfactants
  • Hydrotropes
  • Microemulsions
  • Shape transition
  • Small-angle neutron scattering
  • Supercritical CO<inf>2</inf>


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