Abstract
Bicontinuous microemulsions (BMEs), self-assembly systems consisting of oil and water nanodomains separated by surfactant monolayers, have many applications. However, changes in structure and properties of BMEs in the vertical direction can affect BMEs’ utility. This study's objective was to determine the effect of equilibration time (τeq) on structural changes in the vertical direction for bicontinuous phases of Winsor-III (WIII) systems in situ or after being isolated, for D2O + H2O/1-dodecane/sodium dodecyl sulfate (SDS)/1-pentanol/NaCl at 22 °C. Small-angle neutron scattering (SANS) measurements were performed using a vertical stage sample environment that precisely aligned samples in the neutron beam. SANS data were fitted by the Teubner-Strey (TS) model and changes in TS-derived parameter values were observed. For 10 min ≤ τeq ≤ 4 h, the effective activity of the bicontinuous phase's surfactant monolayers increased with time at all vertical positions. At short equilibration (τeq = 10 min), small but significant amounts of water and oil were transiently emulsified near the WIII upper liquid-liquid interface. WIII systems underwent a relaxation process after being transferred to narrow 1 mm pathlength cells, resulting in a decrease of surfactant activity for the top half of the bicontinuous phase. For isolated bicontinuous phases, results suggest that SDS was desorbed from the BMEs by quartz near the bottom, while near the top, the water concentration near was relatively high. The results suggest that WIII systems should equilibrate for at least 4 hours after being prepared and transferred to a container that differs in cross sectional area and surfactant behavior in BMEs can change near interfaces.
| Original language | English |
|---|---|
| Pages (from-to) | 6109-6119 |
| Number of pages | 11 |
| Journal | Soft Matter |
| Volume | 20 |
| Issue number | 31 |
| DOIs | |
| State | Published - Apr 16 2024 |
Funding
This manuscript has been authored by UT-Battelle, LLC, under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (http://energy.gov/downloads/doe-public-access-plan). Conceptualization of BME experimental design, SANS data acquisition, and interpretation of results was primarily supported as part of the Breakthrough Electrolytes for Energy Storage (BEES), an Energy Frontier Research Center funded by the U.S. Department of Energy (DOE), Office of Science, Basic Energy Sciences (BES) under (award # DE-SC0019409), and is gratefully acknowledged. SANS measurements were performed using the Bio-SANS instrument of the Center for Structural Molecular Biology (FWP ERKP291), a Structural Biology Resource of the U.S. DOE Office of Biological and Environment Research. This research used resources at the High Flux Isotope Reactor, a U. S. DOE Basic Energy Sciences User Facility operated by the Oak Ridge National Laboratory (ORNL). ORNL is operated by UT-Battelle, LLC under contract no. DE-AC05-00OR22725 with the U.S.