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Micro-Emulsion Xiaowen Feng Peking University, Department of Chemistry Outline LOGO 1. Introduction 2. Basic Concepts 3. Characteristic Properties 4. Conclusion YOUR SITE HERE History LOGO 1928 The first commercial microemuls ion by Radawald. 1943 Was recognized as special kind of colloidal dispersion before the work of Schulman. 1958 Be named microemulsions in 1959. 1970 1970, research in microemulsion reached a large scale. YOUR SITE HERE What is Micro Emulsion? LOGO Water Phase Oil Phase Surfactant Co-Surfactant 多为短链醇(611碳) YOUR SITE HERE Concept of Micro Emulsion LOGO Micro Emulsions are dispersions of oil and water made with surfactant, cosurfactant molecules. In many respects, they are small-scale versions of emulsions. However, the droplet sizes are very small, typically 100 A, about 100 times smaller than typical emulsion droplet sizes. YOUR SITE HERE 本征曲率 LOGO a0 v / lc W /O a0 v / lc O /W a0 v / lc 双连续相 YOUR SITE HERE Micro Emulsion in Our Life LOGO The advent of micro emulsion has lead to the improvement in many fields. Food phar macy Micro Emulsion … Catal yst Oil Reco very Daily use Chem istry YOUR SITE HERE Basic Concepts LOGO Micro Emulsion Surfactant Film Micro Emulsion Models YOUR SITE HERE Surfactant Film LOGO As in emulsions it bends spontaneously toward the medium where the surfactant molecule is more soluble (Bancroft rule) This figure explains probably why continuous inversion can be obtained by changing the relative proportions of oil and water in an oil-water-surfactant-alcohol mixture. The alcohol partition coefficient between the surfactant film and oil and water bulk phases can be adjusted to vary Co continuously from positive to negative values. YOUR SITE HERE Surfactant Film LOGO If the surfactant layers contain shortchain alcohols that introduce disorder in the film, K can decrease to about kT and k to about 100 A: long-range order is destroyed and the system remains a micro emulsion. YOUR SITE HERE Micro Emulsion Models LOGO No evidence of the well-defined characteristic size it predicts that two-phase systems with symmetrical o/w and w/o micro emulsions can coexist. Crude. Polyhedral Model ? Cubic Lattice Model A better model is required YOUR SITE HERE Characteristic Properties LOGO Characteristic Interfacial tension Behaves like Newtonian fluids Properties Thermodynamically stable, contrary to emulsions Large value of face area lead to the better function of transport of heat and substance YOUR SITE HERE Interfacial Properties LOGO A particularly important problem was the origin of the ultra low interfacial tensions between the microemulsion and the excess phases. The subject was very controversial, but it is now well established that in most cases the tension is low because the surface pressure of the surfactant monolayer at the interface between the microemulsion and the excess phase is high and almost compensates the bare oil-water interfacial tension. YOUR SITE HERE LOGO YOUR SITE HERE Uses of Micro Emulsion LOGO Microemulsions ave many commercially important uses. The fluid used in some dry cleaning processes is a water-in-oil microemulsion. Some floor polishes and cleaners, personal care products, pesticide formulations, and cutting oils are actually microemulsions. Much of the work done on these systems have been motivated by their possible use to mobilize petroleum trapped in porous sandstone for enhanced oil recovery. A fundamental reason for the uses of these systems is that a microemulsion phase sometimes has an ultralow interfacial tension with a separate oil or aqueous phase, which may release or mobilize them from solid phases even in conditions of slow flow or low pressure gradients. YOUR SITE HERE Uses of Micro Emulsion LOGO Extraction Depurative More and more applications in our life Makeup Nano Science YOUR SITE HERE Conclusion LOGO Microemulsion properties are extremely varied. The extreme diversity of their practical applications is one consequence. One of their disadvantages is the large amount of surfactant required to stabilize them because of the small dispersion size. Although microemulsion properties are beginning to be satisfactorily understood, especially the droplet structure, large research domains remain to be clarified. Whether we should consider the quantum effect in the research of Micro Emulsion ? YOUR SITE HERE LOGO Thank you! Xiaowen Feng E-mail: [email protected] Tel: 13488811898 YOUR SITE HERE