Structural evolution within the one-phase region of a three-component microemulsion system: Water–n-decane–sodium-bis-ethylhexylsulfosuccinate (AOT)

Abstract

Articles you may be interested inPhase field theory of interfaces and crystal nucleation in a eutectic system of fcc structure: I. Transitions in the one-phase liquid region Hard core Yukawa fluid with temperature and density dependent interaction: Phase diagram of the AOT/water/decane microemulsion The density near a critical composition of the AOT-water-decane microemulsionThe continuous inversion from a water-in-oil (w/o) microemulsion at low temperatures to an oil-in-water (o/w) microemulsion at higher temperatures within the one-phase channel of water (0.6% NaCl)-n-decane-AOT microemulsion system is investigated by small angle neutron scattering (SANS). At constant AOT (surfactant) weight fraction r of 12%, the structural evolution as a function of temperature takes place in different forms as the oil-towater weight fraction a is varied from 15 to 90 %. At low o-w weight fractions (a = 15 and 20 %) the microemulsions transform from a water-internal, oil-continuous structure at lower temperatures to an oil-internal, water-continuous droplet structure at higher temperatures jumping across an intermediate region of a lamellar phase (La)' However, at higher o-w weight fractions (a = 80 and 90 %) the evolution goes through a stage of percolation of the water droplets first into extended water clusters, then the structural inversion takes place probably through a transition of these water clusters into an entangled tubular structure. At equal oil-to-water volume ration (a = 40% ), the structure can be described as bicontinuous at both low and high temperatures. In this case we are able to extract two lengths characterizing the structure from SANS data using different models for the scattering length density fluctuation correlation function of a bicontinuous microemulsion.

Protein folding in a reverse micelle environment: The role of confinement and dehydration

“…24 The structure of RMs has been studied with experimental techniques including fluorescence, [25][26][27] NMR, [28][29][30] IR, [31][32][33] and small-angle neutron scattering (SANS)/small-angle x-ray scattering (SAXS). [34][35][36][37][38][39] Scattering studies provide limited insight into the size distribution of the RMs as well as the degree of shape fluctuations. In considering the use of RMs as a confining environment for the study of peptide folding and aggregation, it is important to consider the possible role of RM shape fluctuations in any interpretation of the thermodynamics or kinetics of folding and aggregation.…”

Ionic Liquids in Microemulsions—A Concept To Extend the Conventional Thermal Stability Range of Microemulsions

“…249 The liquid crystalline lamellar phase corresponds to f a = -1. 169 These values delimit the region, where microemulsions may be found.…”

“…Furthermore, the SAXS spectra of both systems were fitted by the Teubner-Strey (TS) model, 161,249 which can be used to describe small angle scattering by microemulsions. A characteristic q -4 dependence of the intensity distribution at large q values can be observed.…”

Aggregate Structure and Dynamic Percolation in Microemulsions

“…This is surprising, as for instance the assumption of a AOT being independent of the size of the droplets might considered to be too simple. In fact it has been discussed that a AOT is weakly dependent on ω [21], the water to oil ratio [22] and also on temperature [5]. Since the polar radius does not appear to depend on molecular parameters of the oil it is expected that to a first approximation the droplet structure is only determined by the ratio of water to surfactant.…”