Emulsions and Microemulsions
Emulsions and microemulsions are both stable dispersions of oil-in-water or water-in-oil. Surfactants are the principal agents that enable oil and water to mix. Emulsions are stable dispersions of immiscible liquids, but they are not thermodynamically stable. We say that they are kinetically stable. These type of dispersions are sometimes called macroemulsions. Microemulsions, on the other hand, are thermodynamically stable. While some people insist that microemulsions must be transparent, that is not really a critical part of their description. In the short course we will give a systematic introduction to the mechanisms of kinetic stabilization of macroemulsions, show how macroemulsions are related to microemulsions, and show how to systematically select a surfactant system to make a stable emulsion or microemulsion.
Articles
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This paper contains a good illustration of how one may go about optimizing a surfactant formulation for creating a stable microemulsion, even when dealing with an "oil" phase that isn't usually thought of as being an oil.
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Illustrates the close connection between the selection of surfactants that make very good emulsifiers and the selection of surfactants that are very efficient at solubilizing oils. Even more exciting is the information that illustrates how simple molecules like fatty alcohols and hydrotropes, which are much less expensive than surfactants, can be used to reduce the amount of surfactant required in an emulsion or microemulsion. Since surfactants are often the most expensive component in an emulsion or microemulsion, this technique can cut your costs and increase your profit.
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How to Formulate Nontoxic Microemulsions
A major barrier to innovation in the consumer products, foods, cosmetics and drug delivery systems is the cost of using any molecules that are not grandfathered into approval by the FDA for such applications. In the following paper, we show how natural emulsifiers and edible surfactants can be combined to emulsify or solubilize just about everything, including industrial solvents!
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What is the Net-Average Curvature Model of Microemulsions?
This last paper deals with an advanced topic: Is it possible to predict the effect of changes of formulation variables on solubilization, emulsion stability, and surfactant requirements? The answer is "yes" and the model is surprisingly easy to use.
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Microemulsion of Mixed Chlorinated Solvents Using Food Grade (Edible) Surfactants
Ground water contamination frequently consists of mixed chlorinated solvents [e.g., tetrachloroethylene (PCE), trichloroethylene (TCE), and trans-1, 2-dichloroethylene (DCE)]. In this research, mixtures of the food grade (edible) surfactants bis(2-ethyIhexyl) sodium sulfosuccinate (AOT) and sodium mono- and dimethylnaphthalene sulfonate (SMONS) were used in the formation of middle-phase microemulsions for mixed chlorinated solvents. Microemulsions of binary (e.g., PCE/TCE, PCE/DCE, DCE/TCE) and ternary (PCE/TCE/DCE) chlorinated solvent systems were evaluated. Several empirical correlations were used for describing and/or predicting the phase behavior of the resulting middle-phase microemulsions (e.g., the ideal mixing rule or the nonideal regular mixing theory).