How to study microemulsions
The application of various experimental techniques for studying the properties of ternary mixtures H2O-oil-nonionic amphiphile is demonstrated. Based on detailed knowledge of the phase behavior, in particular, the positions and extensions of the three-phase bodies, the origin of the ultralow interfacial tensions and strong opalescence of the solutions is elucidated. Within the three-phase body one finds a maximum of the velocity of phase separation of the three phases that is correlated to a minimum of the viscosity and a jump of the electric conductivity. The properties of the homogeneous microemulsions are measured along a path through the phase prism at constant amphiphile concentration but varying oil/water ratio. The dynamics of the microstructure is studied by viscosity, dynamic light scattering, and electric field and pressure jump relaxation, as well as by ultrasonic absorption. The characteristic dimensions of the structure are determined by SANS and SAXS, NMR self-diffusion, electric conductivity, and freeze fracture electron microscopy.
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Cited by (298)
Multi-component phase behavior of biosurfactants
2023, Current Opinion in Colloid and Interface ScienceThe public increasingly requests green formulations as a consequence of growing sustainability awareness. This may include glycolipid and lipopeptide biosurfactants (BS), which are considered renewable, biodegradable, and mild alternatives to conventional fossil-based surfactants. For developing green formulations, it is crucial to understand the phase behavior and the resulting physico-chemical characteristics of systems with BS. This is not only necessary for binary systems of BS in water, which have already been frequently studied and reviewed. But it is also important to study combinations with other surfactants and oils due to their higher relevance for applications. For this reason, we review in this article the different types of phase behavior of systems comprising BS, in particular systems with rhamnolipid, sophorolipid, mannosylerythritol lipid, cellobiose lipid, and surfactin.
Influence of additives on a Pluronic-based cubic phase
2023, Colloids and Surfaces A: Physicochemical and Engineering AspectsIn the present work, the cubic phase of the triblock copolymer with the trade name Pluronic PE6800 is studied with and without additives. The incorporated additives are ionic linear alkylbenzosulfonate, LAS, non-ionic 1,2-propylene glycol and maltose. Small-angle X-ray scattering (SAXS) experiments are performed to characterize the cubic lattice constant and the temperature stability of the cubic phase. In addition, rheology is exploited to study the different samples. Frequency sweeps are performed to investigate the flow properties and stability of the samples at ambient temperature.
Structure, Partitioning, and transport behavior of microemulsion Electrolytes: Molecular dynamics and electrochemical study
2023, Journal of Molecular LiquidsMicroemulsion electrolyte has been proposed as redox flow battery electrolyte to decouple the redox active species’ solubility and conductivity by taking advantage of stabilizing both aqueous and nonaqueous phases in nanoscale. Herein, molecular dynamic (MD) analysis was applied to characterize a family of Tween® 20/1-butanol/KNO3aq/Toluene microemulsions with different compositions, determining their microstructure that tends to adopt under standard conditions and evaluating their stability through total energy evolution. Instead of forming a densely packed surfactant layer that divides aqueous and nonaqueous phases, toluene was trapped in the nonpolar surfactant chain. Based on this finding, we proposed an alternative mathematical expression to correlate surface area-to-volume ratio with correlation length which provided a good accordance between simulation and experimental results. Moreover, the nature of the oil–water interface was revealed by quantitatively analyzing the hydrogen bonds between the surfactant/cosurfactant and the water. Electrochemical analyses are performed to examine how the structures of microemulsion electrolytes correlate to their electrochemical performance. The results indicate that absorption on the electrode surface, ionic conductivity, and connectivity of both aqueous and nonaqueous phases are of central significance in affecting the redox reaction. These findings, therefore, shed light on guiding the formulation of microemulsion electrolytes and regulating their electrochemical performance as electrolytes for redox flow battery applications. In the end, we proposed an electrochemical reaction mechanism of Fc in the microemulsion electrolyte.
Fish-shaped diagram of liquid–liquid equilibria for the mixtures water + n-alkane + n-alkyl polyglycol ether
2022, Fluid Phase EquilibriaThe aim of this work is to determine the fish-shaped diagram of liquid–liquid equilibria (LLE) of ternary mixtures of water + n-alkane + n-alkyl polyglycol ether (CiEj) using a cloud point method with laser scattering technique. n-Octane and n-dodecane were selected as the n-alkanes, and 2-butoxyethanol (C4E1) and 2-(2-hexyloxyethoxy)ethanol (C6E2) were selected as the n-alkyl polyglycol ethers. In the measurements of the ternary mixtures, the CiEj free basis mass fraction “α” of n-alkane was changed from 0.1 to 0.9. The experimental fish-shaped diagrams were evaluated by comparing the experimental cloud point data with the fish-shaped diagrams as well as the phase boundaries of tie-line and tie-triangle data in the mixtures of water + n-octane + C4E1 and water + n-dodecane + C6E2 reported in the literature. X-points where the fish body and fish tail intersect were determined from the experimental cloud points, as well as the upper and lower critical point temperature of the fish-body. Changes in the phase diagram and X-points with different n-alkanes, CiEj, and the value of α were analyzed using the experimental data. The LLE data of the mixture of water + C6E2, as one of the binary components of the ternary mixture, was also measured.
Fast-track realization of reactive microemulsion systems – Systematic system analysis and tailored application of PSE methods
2022, Chemical Engineering ScienceDespite the overarching necessity for sustainability, the realization of novel process concepts using innovative green reaction media, such as microemulsions is still hindered by their inherent complexity. To overcome this, a holistic guideline for the fast-track realization of microemulsion systems is presented and applied on a mini-plant for the hydroformylation of 1-dodecene in microemulsions. It combines a rigorous system analysis and identification of challenges for process design and operation. Here, critical unmeasurability of concentrations, small feasible operation regions, and a highly dynamic system behavior are identified. This is encountered by tailored PSE methods: a dynamic model for the complex three-phasic separation of microemulsions, the formulation of a concentration soft-sensor, as well as multi-rate moving horizon state estimation and subsequent dynamic real-time optimization. Applying those, stable operation of the mini-plant for up to 200 h is ensured together with a steady-state product yield of 38% and a product selectivity of 92%.
Microemulsion and its application: An inside story
2021, Materials Today: ProceedingsMicroemulsion is one of the complex form of surfactant self-assemblies in an oil–water environment. Solubilization of oil in water has a resourceful use in foodstuffs (dairy product), agricultural sprays and pharmaceutical preparations as they are less expensive. In food industry, microemulsion promotes solubilization of insoluble nutrients in non-polar solvent. It also finds application in polymerization and chemical reactions as media and vehicles, by introducing reactants in nanosized water droplets. Microdomains within a microemulsion compartmentalizes reactants thereby enhancing net reaction rate or protect nutrients within it from degradation or oxidation by light, heat or oxygen. It is used as a media in electrochemical reactions, cosmetics and cleaning product formulation. Reverse micelles using environment friendly non-ionic surfactants are used as nanoreactors to synthesize iron nanoparticles, which can be used in environmental contaminants remediation. In the pharmaceutical field, microemulsion is used for sustained drug delivery and improved drug bioavailability. They may be used as the carrier for protein and peptide delivery to the GI tract. Degradation of proteins is effectively reduced due to the use of relatively mild conditions during the formulation process of microemulsions. There have been large international efforts towards understanding the phases of a microemulsion because of the possibility of using them to increase the yield from vast oil reserves in capillary rocks (enhanced oil recovery), cutting oils, lubrication etc. The objective of this review is to present the basics of microemulsion, its classification on various basis and its possible application in chemical, industrial and biological arena. Herein the concept, types and formation mechanism of microemulsion are primarily introduced. It has been classified on the basis of structural point of view and also on the basis of the components point of view. Due to its versatile properties like ultralow interfacial tension, large interfacial area and capacity to solubilize both aqueous and oil soluble compounds, microemulsion have varied applications.