Micro-Emulsion Xiaowen Feng Peking University, Department of Chemistry

YOUR SITE HERE LOGO 1. Introduction 2. Basic Concepts 3. Characteristic Properties 4. Conclusion Outline

YOUR SITE HERE LOGO History The first commercial microemuls ion by Radawald. Was recognized as special kind of colloidal dispersion before the work of Schulman. Be named microemu- lsions in , research in microemu- lsion reached a large scale.

YOUR SITE HERE LOGO What is Micro Emulsion? Surfactant Oil Phase Water Phase Co-Surfactant 多为短链醇（ 碳）

YOUR SITE HERE LOGO Concept of Micro Emulsion  Micro Emulsions are dispersions of oil and water made with surfactant, co- surfactant 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 LOGO 本征曲率

YOUR SITE HERE LOGO The advent of micro emulsion has lead to the improvement in many fields. Micro Emulsion Food phar macy … Daily use Chem istry Oil Reco very Catal yst Micro Emulsion in Our Life

YOUR SITE HERE LOGO Basic Concepts Micro Emulsion Surfactant Film Micro Emulsion Models

YOUR SITE HERE LOGO Surfactant Film 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 LOGO Surfactant Film If the surfactant layers contain short- chain alcohols that introduce disorder in the film, K can decrease to about kT and to about 100 A: long-range order is destroyed and the system remains a micro emulsion.

YOUR SITE HERE LOGO Micro Emulsion Models ? 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. A better model is required Polyhedral Model Cubic Lattice Model

YOUR SITE HERE LOGO Characteristic Properties Properties Behaves like Newtonian fluids Characteristic Interfacial tension Thermodynamically stable, contrary to emulsions Large value of face area lead to the better function of transport of heat and substance

YOUR SITE HERE LOGO Interfacial Properties  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.

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YOUR SITE HERE LOGO Uses of Micro Emulsion  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 LOGO Uses of Micro Emulsion More and more applications in our life Nano Science Makeup Depurative Extraction

YOUR SITE HERE LOGO Conclusion  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 Tel: