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Emulsions and Microemulsions

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Emulsion:

A dispersion of droplets of one liquid

in another, immiscible liquid

Macroemulsions (d > 1000 nm)

Miniemulsions (100 nm < d < 1000 nm)

Microemulsions ( 10 nm < d < 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 sur factants only !!

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Droplet stabilization

Electrostatic stabilization

Steric stabilization

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How one can come to smalldroplets ?

Macroemulsions (d > 1000nm)

Mechanism of emulsification:

- adsorption

(increase of the surfactant concentration)

- spreading

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How one can come to smallerdroplets ?

Miniemulsions (100 nm < d < 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 muchsmallerdroplets ?

Microemulsions ( 10 < d < 100 nm)

- Thermodynamically stabledispersion of

one liquid phase into another, stabilizedby 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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HoSpontaneous 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, surfactantand co-surfactant

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w/o - microemulsion + water soluble polymer

Polymer induced cluster formation

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Polyelectrolyte-modified microemulsions

Oppositely

charged PEL can

be incorporated !!

PEL increase the

stability of thesurfactant 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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Polyelectrolyte-modified microemulsions

as nanoreactors ?

PEL can control the

particle growing

process ???

PEL can stabilize

nanoparticles

during the processof redispersion ???

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Iso lat ion of po lymer-stabi l ized nanopart ic les

(patent: WO2004/056928AS)

Nanoparticle formation in w/o microemulsions

Solvent evaporation

Redispersion of the polymer-stabiliziednanoparticles