Miniemulsion

A miniemulsion (also known as nanoemulsion) is a special case of emulsion. A miniemulsion is obtained by shearing a mixture comprising two immiscible liquid phases (for example, oil and water), one or more surfactants and, possibly, one or more co-surfactants (typical examples are hexadecane or cetyl alcohol).

IUPAC definition

Emulsion in which the particles of the dispersed phase have
diameters in the range from approximately 50 nm to 1 μm.

Note 1: Mini-emulsions are usually stabilized against diffusion degradation
(Ostwald ripening (ref.[1] )) by a compound
insoluble in the continuous phase.

Note 2: The dispersed phase contains mixed stabilizers, e.g., an ionic
surfactant, such as sodium dodecyl sulfate (n-dodecyl sulfate sodium) and
a short aliphatic chain alcohol (“co-surfactant”) for colloidal stability, or a
water-insoluble compound, such as a hydrocarbon (“co-stabilizer” frequently
and improperly called a “co-surfactant”) limiting diffusion degradation.
Mini-emulsions are usually stable for at least several days.[2]

The shearing proceeds usually via exposure to high power ultrasound[3][4][5] of the mixture or with a high-pressure homogenizer, which are high-shearing processes. In an ideal miniemulsion system, coalescence and Ostwald ripening are suppressed thanks to the presence of the surfactant and co-surfactant.[3]

Stable droplets are then obtained, which have typically a size between 50 and 500 nm. Miniemulsion-based processes are, therefore, particularly adapted for the generation of nanomaterials. There is a fundamental difference between traditional emulsion polymerisation and a miniemulsion polymerisation. Particle formation in the former is a mixture of micellar and homogeneous nucleation, particles formed via miniemulsion however are mainly formed by droplet nucleation.

References

  1. ↑ Richard G. Jones, Edward S. Wilks, W. Val Metanomski, Jaroslav Kahovec, Michael Hess, Robert Stepto, Tatsuki Kitayama, ed. (2009). Compendium of Polymer Terminology and Nomenclature (IUPAC Recommendations 2008) ("The Purple Book"). RSC Publishing. ISBN 978-1-84755-942-5.
  2. ↑ "Terminology of polymers and polymerization processes in dispersed systems (IUPAC Recommendations 2011)" (PDF). Pure and Applied Chemistry 83 (12): 2229–2259. 2011. doi:10.1351/PAC-REC-10-06-03.
  3. 1 2 Mason TG, Wilking JN, Meleson K, Chang CB, Graves SM, "Nanoemulsions: formation, structure, and physical properties", Journal of Physics: Condensed Matter, 2006, 18(41): R635-R666
  4. ↑ Peshkovsky A, Peshkovsky S, "Acoustic Cavitation Theory and Equipment Design Principles for Industrial Applications of High-Intensity Ultrasound", Physics Research and Technology, Nova Science Pub. Inc., October 31, 2010, ISBN 1-61761-093-3
  5. ↑ "Translucent Oil-in-Water Nanoemulsions", Industrial Sonomechanics, LLC, 2011
    "Nanoemulsions Used for Parenteral Nutrition", Industrial Sonomechanics, LLC, 2011
    "Drug-Carrier Liposomes and Nanoemulsions", Industrial Sonomechanics, LLC, 2011
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