Emulsions and Microemulsions

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Emulsions and Microemulsions
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EmulsionA dispersion of droplets of one liquid
in another, immiscible liquid

• Macroemulsions (d gt 1000 nm)
• Miniemulsions (100 nm lt d lt 1000 nm)
• Microemulsions ( 10 nm lt d lt 100 nm)

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Oil and Water do not mix !!
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What we need for making macroemulsions ?

• Emulsifier May make it easier to form a
  macroemulsion and provide stability against
  aggregation, e.g. surfactants or polymers

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Some special effects of surfactants

• Decrease of surface tension
• Control of the type of emulsion
• Droplet stabilization

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Decrease of surface tension

• Decrease of the energy input !

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Control of the type of emulsion

• HLB - value
• (Hydrophilic-Lipophilic-Balance)
• HLB 20 M hydrophilic part / M total
• ? For nonionic surfactants only !!

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Droplet stabilization

• Electrostatic stabilization
• Steric stabilization

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How one can come to small droplets ?

• Macroemulsions (d gt 1000nm)
• Mechanism of emulsification
• - adsorption
• (increase of the surfactant concentration)
• - spreading

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How one can come to smaller droplets ?

• Miniemulsions (100 nm lt d lt 1000nm)
• - increase of the surfactant concentration
• - increase of the energy input !!
• (e.g. ultrasound treatment)
• - addition of hydrophobic agents
• (supress of Ostwald ripening)

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Laplace pressure (? pLaplace)

• ? pLaplace 2 ? / r
• ? - surface tension
• r radius of the droplet

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How one can come to much smaller droplets ?

• Microemulsions ( 10 lt d lt 100 nm)
• - Thermodynamically stable dispersion of one
  liquid phase into another, stabilized by an
  interfacial film.

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Microemulsions

• Isotropic, optically clear
• Thermodynamically stable
• Newtonian-flow behaviour
• Low surface tension
• Reversible temperature behaviour
• Droplet size between 10 and 100 nm
• (o/w w/o bicontinuous)

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Microemulsions are thermodynamically stable !
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Ho Spontaneous Curvature of the surfactant film

• The most essential parameter
• of the system !!

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Microemulsions (ternary systems)

• water, oil, surfactant

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Microemulsions (quaternary systems)

• water, oil, surfactant
• and co-surfactant

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Polymer induced cluster formation
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Polyelectrolyte-modified microemulsions

• Oppositely charged PEL can be incorporated !!
• ? PEL increase the stability of the surfactant
  film !!

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Fields of application

• Microemulsions as nanosize reactor
• Microemulsions in separation processes
• Microemulsions as drug delivery systems
• Microemulsions in enhanced oil recovery

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w/o Microemulsion I
w/o Microemulsion II
containing e.g. 1mM BaCl2
containing e.g. 1mM Na2SO4
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Polyelectrolyte-modified microemulsions as
nanoreactors ?
PEL can control the particle growing process ???

• PEL can stabilize nanoparticles during the
  process of redispersion ???

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Isolation of polymer-stabilized nanoparticles
(patent WO2004/056928AS)
Nanoparticle formation in w/o microemulsions
Solvent evaporation
Redispersion of the polymer-stabilizied
nanoparticles