Transcript Micro-Emulsion

Micro-Emulsion
Xiaowen Feng
Peking University, Department of Chemistry
Outline
LOGO
1. Introduction
2. Basic Concepts
3. Characteristic
Properties
4. Conclusion
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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.
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What is Micro Emulsion?
LOGO
Water Phase
Oil Phase
Surfactant
Co-Surfactant
多为短链醇（611碳）
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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.
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本征曲率
LOGO
a0  v / lc
W /O
a0  v / lc
O /W
a0  v / lc
双连续相
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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
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Basic Concepts
LOGO
Micro Emulsion
Surfactant
Film
Micro
Emulsion
Models
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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.
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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.
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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
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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
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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.
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LOGO
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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.
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Uses of Micro Emulsion
LOGO
Extraction
Depurative
More and more
applications in
our life
Makeup
Nano Science
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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 ?
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LOGO
Thank you!
Xiaowen Feng
E-mail: [email protected]
Tel: 13488811898
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