Structure of high internal phase aqueous-in-oil emulsions and related inverse Micelle Solutions. 3. Variation of surfactant

dc.contributor.authorReynolds, Philip
dc.contributor.authorGilbert, Elliot P
dc.contributor.authorHenderson, Mark
dc.contributor.authorWhite, John
dc.date.accessioned2015-12-10T22:39:50Z
dc.date.issued2009
dc.date.updated2016-02-24T10:43:02Z
dc.description.abstractThe small angle neutron scattering from high internal phase water-in-hexadecane and saturated ammonium nitrate-in-hexadecane emulsions is compared with that from related hexadecane-based inverse micellar solutions. Three molecular weights of the monodisperse polyisobutylene acid amide (PIBSA) surfactant 750, 1200, and 1700 were studied over a range of surfactant concentrations. As an additional comparison, emulsions based on sorbitan monooleate and isostearate surfactants were investigated. The scattering from molecular weight 1200 water-based PIBSA emulsions can be fitted at all concentrations to a model with a surfactant coated aqueous droplet-oil interface together with the majority of the surfactant in the oil phase of the emulsion in the form of inverse micelles. Variation of the molecular weight shows a variety of phases of increasing curvature: lamellar, sponge, and, most commonly, the emulsion structure described above. In addition, the molecular weight affects the oil component in the emulsions, which can contain either cylindrical micelles or spherical micelles of varying water but constant hexadecane content. Increased phase curvature is favored by both increased PIBSA molecular weight and ammonium nitrate dissolved in the water. These observations are consistent with "Wedge theory". The structures observed in the emulsions are close to those observed in related inverse micellar solutions made from hexadecane, the surfactant, and water. Lower concentrations of surfactant in the micellar solutions decrease micelle curvature, except where the inverse micelles are spherical and small; here, there is little effect of dilution. Substitution of sorbitan surfactants for PIBSAs produces slightly less organized but similar structures, with smaller spherical micelles containing proportionally more water. The aqueous-oil droplet interface has a relatively invariant monolayer of adsorbed surfactant. For all emulsions, we can infer from the mass balance that micelle concentrations are depressed in the inverse micellar solutions because up to half the added surfactant is present as individually dissolved molecules.
dc.identifier.issn1520-6106
dc.identifier.urihttp://hdl.handle.net/1885/57358
dc.publisherAmerican Chemical Society
dc.sourceJournal of Physical Chemistry B
dc.subjectKeywords: Ammonium nitrate; Aqueous droplets; Cylindrical micelles; Emulsion structures; Hexadecane; Internal phase; Inverse micelles; Mass balance; Micellar solution; Micelle concentrations; Monodisperse; Oil components; Oil droplets; Oil emulsions; Oil phase; Pha
dc.titleStructure of high internal phase aqueous-in-oil emulsions and related inverse Micelle Solutions. 3. Variation of surfactant
dc.typeJournal article
local.bibliographicCitation.issue36
local.bibliographicCitation.lastpage12242
local.bibliographicCitation.startpage12231
local.contributor.affiliationReynolds, Philip, College of Physical and Mathematical Sciences, ANU
local.contributor.affiliationGilbert, Elliot P, College of Physical and Mathematical Sciences, ANU
local.contributor.affiliationHenderson, Mark, College of Physical and Mathematical Sciences, ANU
local.contributor.affiliationWhite, John, College of Physical and Mathematical Sciences, ANU
local.contributor.authoremailu8506305@anu.edu.au
local.contributor.authoruidReynolds, Philip, u9400730
local.contributor.authoruidGilbert, Elliot P, u3800238
local.contributor.authoruidHenderson, Mark, u4022796
local.contributor.authoruidWhite, John, u8506305
local.description.embargo2037-12-31
local.description.notesImported from ARIES
local.identifier.absfor030603 - Colloid and Surface Chemistry
local.identifier.ariespublicationu4217927xPUB397
local.identifier.citationvolume113
local.identifier.doi10.1021/jp903484j
local.identifier.scopusID2-s2.0-69949126490
local.identifier.thomsonID000269655300010
local.identifier.uidSubmittedByu4217927
local.type.statusPublished Version

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