Transition from a foam-like to an onion-like nanostructure in water-rich L3 phases
Author:
Menold Philipp1, Strey Reinhard2, Roitsch Stefan2, Preisig Natalie1, Stubenrauch Cosima1
Affiliation:
1. Institute of Physical Chemistry , University of Stuttgart , Pfaffenwaldring 55, 70569 Stuttgart , Germany 2. Institute of Physical Chemistry , University of Cologne , Luxemburger Straße 116, 50939 Cologne , Germany
Abstract
Abstract
In dilute water-surfactant systems L3 phases are found in which bilayers interconnect to form a sample-spanning sponge-like structure. From our previous study of the system water/NaCl-AOT (sodium bis(2-ethylhexyl) sulfosuccinate) we know that a transition of this sponge-like structure to an oil-continuous foam-like structure occurs upon addition of minute amounts of oil (about 3 wt%, α = 0.03) in the L3 channel at a constant surfactant mass fraction of γ = 0.15 and T = 25 °C. The aim of the present study was to verify if the same transition occurs at γ = 0.25. To achieve this goal, we determined the relevant part of the phase diagram and studied the electrical conductivities and viscosities within the narrow one-phase L3 channel. Although the electrical conductivities and viscosities change qualitatively like those observed at γ = 0.15 we did not observe a sponge-like structure at γ = 0.25 in the oil-free system (α = 0) with freeze-fracture electron microscopy (FFEM) and freeze fracture direct imaging (FFDI). Together with the FFEM/FFDI images and SANS/SAXS curves we provide experimental evidence for a structural transition with decreasing oil content from a thermodynamically stable foam-like to a thermodynamically stable onion-like nanostructure at γ = 0.25 rather than to a sponge-like structure as is the case at γ = 0.15.
Publisher
Walter de Gruyter GmbH
Subject
Condensed Matter Physics,General Chemical Engineering,General Chemistry
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