1. Emulsions and Microemulsions

2. 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)

3. Oil and Water do not mix !!

4. 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

5. Some special effects of surfactants
Decrease of surface tension
„Control“ of the type of emulsion
Droplet stabilization

6. Decrease of surface tension
Decrease of the energy input !

7. „Control“ of the type of emulsion
HLB - value
(Hydrophilic-Lipophilic-Balance)
HLB = 20 M hydrophilic part / M total
 For nonionic surfactants only !!

8. Droplet stabilization
Electrostatic stabilization
Steric stabilization

9. How one can come to small droplets ?
Macroemulsions (d > 1000nm)
Mechanism of emulsification:
- adsorption
(increase of the surfactant concentration)
- spreading

10. How one can come to smaller droplets ?
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“)

11. Laplace pressure ( pLaplace)
 pLaplace = 2  / r
 - surface tension
r– radius of the droplet

12. How one can come to much smaller droplets ?
Microemulsions ( 10 < d < 100 nm)
- Thermodynamically stable dispersion of one liquid phase into another, stabilized by an interfacial film.

13. 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)

14. Microemulsions are thermodynamically stable !

15. Ho – Spontaneous Curvature of the surfactant film
The most essential parameter
of the system !!

16. Microemulsions (ternary systems)
water, oil, surfactant

17. Microemulsions (quaternary systems)
water, oil, surfactant
and co-surfactant

18. Polymer induced cluster formation
w/o - microemulsion
+ water soluble polymer

19. Polyelectrolyte-modified microemulsions
Oppositely charged PEL can be incorporated !!
 PEL increase the stability of the surfactant film !!

20. Fields of application Microemulsions as nanosize reactor
Microemulsions in separation processes
Microemulsions as drug delivery systems
Microemulsions in enhanced oil recovery

21. Mix Microemulsion I and II
w/o Microemulsion I
w/o Microemulsion II
containing
e.g. 1mM BaCl2
BaSO4 nanoparticle formation!
Precipitation
Mix Microemulsion I and II
Collision and coalescence of droplets
containing
e.g. 1mM Na2SO4

22. Polyelectrolyte-modified microemulsions as nanoreactors ?
• PEL can control the particle growing process ???
PEL can stabilize nanoparticles during the process of redispersion ???

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