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Emulsions and Microemulsions

Emulsions and Microemulsions. 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). Oil and Water do not mix !!. What we need for making macroemulsions ?.

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Emulsions and Microemulsions

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

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

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