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, eds. (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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