Microemulsions:  a qualitative thermodynamic approach

Kahlweit, M.; Strey, R.; Busse, G.

doi:10.1021/j100373a006

Cited by 303 publications

(259 citation statements)

References 2 publications

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“…31 This indicates the "groove" in the multiphase window caused by the existence of the three-phase region is relatively sharp, suggesting the domains are well segregated. 32 This is consistent with the PEO/PEP* coexistence curve shown in Figure 3 which predicts very little mixing at 80°C. However, as noted in section 3, the samples that are believed to be bicontinuous microemulsion in equilibrium with a homopolymer-rich fluid were slightly turbid.…”

Section: Discussionsupporting

confidence: 87%

Ternary Polymer Blends as Model Surfactant Systems

2000

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An investigation of the ternary phase prism for low molecular weight poly(ethylene oxide), squalane, and poly(ethylene oxide-b-ethylenepropylene) is presented. Comparisons are made between this ternary polymer system and classic water/oil/surfactant mixtures to establish further a universal phase diagram description for amphiphilic systems. A combination of visual isothermal measurements, small-angle X-ray scattering, smallangle neutron scattering, and dynamical mechanical spectrometry was used to characterize phases and determine phase boundaries. A rich phase diagram was revealed, including most of the equilibrium liquid crystalline phases associated with diblock copolymers, regions of two-phase and three-phase coexistence, and a bicontinuous microemulsion. Differences between this polymer phase diagram and those from water/oil/ surfactant systems highlight the strong effect of water in the latter.

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Section: Discussionsupporting

confidence: 87%

Ternary Polymer Blends as Model Surfactant Systems

2000

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“…It should be mentioned that in a few cases very low interfacial tensions can be reached and microemulsions can be formed with a single surfactant without cosurfactant. This occurs in particular with double chain ionic surfactants [8,9] and with some non-ionic surfactants [10] Since the surfactant concentration used in preparing microemulsions (several %) is larger than most cmc's 1%) the final interfacial area in microemulsions is proportional to the amount of surfactant used, but the nature of the microemulsion (0/W, W/0 or bicontinuous) does not depend on the amount of surfactant. So long as not yet enough interfacial area has been created to accommodate all available surfactant, some surfactant remains free and the interfacial tension may be negative, thus explaining spontaneous formation of the microemulsion, as is often observed.…”

Section: At Intermediate Concentrations the Adsorption Is Oftenmentioning

confidence: 99%

“…There is no analytical solution for the PB equation for a curved interface, but in case the curvature is weak an expansion in inverse powers of the reduced radius of curvature K a (a = radius of curvature) can be carried out [40 43]. For the negative adsorption inside a highly charged spherical surface this leads to [44] where (10) q = .62+1 = cosh (P0/2) . (11) For low potentials and charge densities Eq.…”

Section: Mvp Hi:11j141j11mentioning

confidence: 99%

Phase Behavior of Ionic Microemulsions

Lekkerkerker

Kegel

Overbeek

1996

Ber Bunsenges Phys Chem

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Non-polar oils and water can form thermodynamically stable quasi-homogeneous (colloidal) mixtures (called microemulsions) in the presence of relatively large amounts (several %) of ionic surfactants. If the surfactant contains a single hydrocarbon chain (e.g. Sodium Dodecyl Sulphate) the presence of a non-ionic cosurfactant (e.g. hexanol) and electrolyte (concentration of the order 0.1 M) is essential. With a double chain surfactant (e.g. Aerosol OT) the cosurfactant can be missed. At increasing concentrations of electrolyte and/or cosurfactant the nature of the microemulsion changes from droplets of oil in water via a presumably bicontinuous pattern to droplets of water in oil. It should be obvious that thermodynamic stability requires the interfacial tension between water and oil to be low (order of 0.01 0.1 mN m -1) so that the dispersion entropy can offset the interfacial free energy. At these low interfacial tensions the influence of curvature on the interfacial tensions becomes important. It turns out that a given amount of surfactant (and co-surfactant) can only disperse a limited amount of oil in water or of water in oil or of water and oil into one another and therefore a microemulsion may be in equilibrium with non colloidal oil and/or water phases. In the bicontinuous microemulsion oil and water may have a geometrically irregular interface or they may form lamellae of more or less constant thickness or other structures, such as a "molten cubic phase". These equilibria lead to very interesting, but rather complicated phase diagrams. It will be discussed by what mechanisms the various components of the mixture influence the interfacial tension and promote the stability of the microemulsion and how this depends on the chemical nature of the components.

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“…The single-phase microemulsion region is called Winsor-type IV phase. To represent these four phases, another notation system, especially employed by Kahlweit et al (1990), uses the symbols 2; 2; 3 and 1, respectively. The factors that affect the phase transition between different types of systems include the salinity, temperature, molecular structure and nature of the surfactant and cosurfactant and the nature of the oil and water-oil ratio (WOR) (Shah 1985).…”

Section: Introductionmentioning

confidence: 99%

Microemulsions: a novel approach to enhanced oil recovery: a review

Bera

Mandal

2014

J Petrol Explor Prod Technol

219

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The trend of growing interest in alternative source of energy focuses on renewable products worldwide. However, the situation of petroleum industries in many countries needs much concern in improving the oil recovery technique. Chemical method, especially microemulsion flooding, plays an important role in enhanced oil recovery technique due to its ability to reduce interfacial tension between oil and water to a large extent as well as alter wettability of reservoir rocks. Surfactant-based chemical systems have been reported in many academic studies and their technological implementations are potential candidates in enhanced oil recovery activities. This paper reviews the role of different types of surfactants in enhanced oil recovery, structure of microemulsion, phase behavior of oil-brine-surfactant/cosurfactant systems with variation of different parameters such as salinity, temperature, pressure and physicochemical properties of microemulsions including solubilization capacity, interfacial tension, viscosity and density under reservoir conditions. The enhanced oil productivity by microemulsion flooding with different surfactant/cosurfactant systems has also been discussed in this paper. This review introduces a new opening in enhanced oil recovery by microemulsion flooding with some new aspects.

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Microemulsions: a qualitative thermodynamic approach

Cited by 303 publications

References 2 publications

Ternary Polymer Blends as Model Surfactant Systems

Ternary Polymer Blends as Model Surfactant Systems

Phase Behavior of Ionic Microemulsions

Microemulsions: a novel approach to enhanced oil recovery: a review

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