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Micro-EmulsionXiaowen FengPeking University, Department of Chemistry
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1. Introduction1. Introduction
2. Basic Concepts2. Basic Concepts
3. Characteristic Properties3. Characteristic Properties
4. Conclusion4. Conclusion
Outline
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History
1928 1943 1958 1970
The first commercialmicroemulsion by Radawald.
Was recognized as special kindof colloidal dispersion before the work of Schulman.
Be named microemu-lsions in 1959.
1970, research in microemu-lsion reached a large scale.
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What is Micro Emulsion?
Surfactant
Oil Phase
Water Phase
Co-Surfactant多为短链醇（ 6-11碳）
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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.
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本征曲率
0 / ca v l
0 / ca v l
/W O0 / ca v l
/O W
双连续相
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The advent of micro emulsion has lead to the improvement in many fields.
Micro Emulsion
Foodpharmacy
…
Daily use
Chemistry
Oil Recov
ery
Catalyst
Micro Emulsion in Our Life
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Basic Concepts
Micro Emulsion
Surfactant Film
Micro Emulsion Models
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Surfactant Film
As in emulsions it bends spontaneouslytoward the medium where the surfactant molecule ismore soluble (Bancroft rule)
This figure explains probably why continuous inversion can beobtained by changing the relative proportions of oil andwater in an oil-water-surfactant-alcohol mixture. Thealcohol partition coefficient between the surfactant filmand oil and water bulk phases can be adjusted to varyCo continuously from positive to negative values.
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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.
k
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Micro Emulsion Models
?
No evidence of the No evidence of the well-defined well-defined
characteristic sizecharacteristic size
it predicts that two-phase systems with symmetrical o/w and w/o micro emulsions
can coexist. Crude.
A better model is A better model is requiredrequired
Polyhedral Model
Cubic Lattice Model
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Characteristic Properties
PropertiesPropertiesBehaves like Newtonian fluids
Characteristic Interfacial tension
Thermodynamically stable, contrary to emulsions
Large value of face area lead to the betterfunction of transport of heat and substance
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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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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.
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Uses of Micro Emulsion
More and more applications in our life
Nano Science
Makeup
Depurative
Extraction
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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 ?
