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Title: Observation of a structural gradient in Winsor-III microemulsion systems

Abstract

Here, we demonstrate here for the first time via small-angle neutron scattering (SANS) that the middle, bicontinuous microemulsion (BμE) phase of Winsor-III systems undergoes a gradual change of structure and composition in the vertical direction, contrary to the commonly held belief of uniform structure and composition. A vertical stage was deployed to enable precise alignment of a custom-designed rectangular cell containing the W III system with respect to the neutron beam, allowing for several different vertical positions to be analyzed. For the water/AOT/CK-2,13 (two-tailed alkyl ethoxylate containing a 1,3-dioxolane linkage)/heptane Winsor-III system, the quasi-periodic repeat distance ( d) and correlation length (ξ), obtained from the Teubner–Strey model applied to the SANS data, decreased and the surface area per volume of the surfactant monolayer ( via Porod analysis) increased in the downward direction, trends that reflect an increase of surfactant concentration, consistent with the ultralow interfacial tension that often occurs for the lower liquid–liquid interface of many W III systems. The water/sodium dodecyl sulfate (SDS)/1-pentanol/dodecane system shared the same trend with regard to d as observed for AOT/CK-2,13. In contrast, for SDS/pentanol, ξ increased and the amphiphilicity factor ( f a) decreased in the downward direction, trends consistent with a decreasemore » of cosurfactant (pentanol) concentration in the downward direction. Non-uniformity in the vertical direction has implications in the transport of solutes between W III phases during the extractive purification of proteins or the removal of heavy metals and pollutants from wastewater, or the deposition of BμEs onto hydrophilic vs. hydrophobic surfaces as thin coatings.« less

Authors:
ORCiD logo [1]; ORCiD logo [2]; ORCiD logo [2]; ORCiD logo [2];  [2]
  1. Univ. of Tennessee, Knoxville, TN (United States)
  2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
OSTI Identifier:
1489100
Alternate Identifier(s):
OSTI ID: 1441225
Grant/Contract Number:  
AC05-00OR22725; 6552
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Soft Matter
Additional Journal Information:
Journal Volume: 14; Journal Issue: 25; Journal ID: ISSN 1744-683X
Publisher:
Royal Society of Chemistry
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS

Citation Formats

Hayes, Douglas G., Pingali, Sai Venkatesh, O’Neill, Hugh M., Urban, Volker S., and Ye, Ran. Observation of a structural gradient in Winsor-III microemulsion systems. United States: N. p., 2018. Web. doi:10.1039/c8sm00322j.
Hayes, Douglas G., Pingali, Sai Venkatesh, O’Neill, Hugh M., Urban, Volker S., & Ye, Ran. Observation of a structural gradient in Winsor-III microemulsion systems. United States. doi:10.1039/c8sm00322j.
Hayes, Douglas G., Pingali, Sai Venkatesh, O’Neill, Hugh M., Urban, Volker S., and Ye, Ran. Mon . "Observation of a structural gradient in Winsor-III microemulsion systems". United States. doi:10.1039/c8sm00322j.
@article{osti_1489100,
title = {Observation of a structural gradient in Winsor-III microemulsion systems},
author = {Hayes, Douglas G. and Pingali, Sai Venkatesh and O’Neill, Hugh M. and Urban, Volker S. and Ye, Ran},
abstractNote = {Here, we demonstrate here for the first time via small-angle neutron scattering (SANS) that the middle, bicontinuous microemulsion (BμE) phase of Winsor-III systems undergoes a gradual change of structure and composition in the vertical direction, contrary to the commonly held belief of uniform structure and composition. A vertical stage was deployed to enable precise alignment of a custom-designed rectangular cell containing the WIII system with respect to the neutron beam, allowing for several different vertical positions to be analyzed. For the water/AOT/CK-2,13 (two-tailed alkyl ethoxylate containing a 1,3-dioxolane linkage)/heptane Winsor-III system, the quasi-periodic repeat distance (d) and correlation length (ξ), obtained from the Teubner–Strey model applied to the SANS data, decreased and the surface area per volume of the surfactant monolayer (via Porod analysis) increased in the downward direction, trends that reflect an increase of surfactant concentration, consistent with the ultralow interfacial tension that often occurs for the lower liquid–liquid interface of many WIII systems. The water/sodium dodecyl sulfate (SDS)/1-pentanol/dodecane system shared the same trend with regard to d as observed for AOT/CK-2,13. In contrast, for SDS/pentanol, ξ increased and the amphiphilicity factor (fa) decreased in the downward direction, trends consistent with a decrease of cosurfactant (pentanol) concentration in the downward direction. Non-uniformity in the vertical direction has implications in the transport of solutes between WIII phases during the extractive purification of proteins or the removal of heavy metals and pollutants from wastewater, or the deposition of BμEs onto hydrophilic vs. hydrophobic surfaces as thin coatings.},
doi = {10.1039/c8sm00322j},
journal = {Soft Matter},
number = 25,
volume = 14,
place = {United States},
year = {Mon May 21 00:00:00 EDT 2018},
month = {Mon May 21 00:00:00 EDT 2018}
}

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Works referenced in this record:

Reduction and analysis of SANS and USANS data using IGOR Pro
journal, November 2006