Global InformationMacroemulsion information
Macroemulsions are dispersed liquid-liquid, thermodynamically unstable systems with particle sizes ranging from 1 to 100 μm (orders of magnitude), which, most often, do not form spontaneously. Macroemulsions scatter light effectively and therefore appear milky, because their droplets are greater than a wavelength of light.[1] They are part of a larger family of emulsions along with miniemulsions (or nanoemulsions). As with all emulsions, one phase serves as the dispersing agent. It is often called the continuous or outer phase. The remaining phase(s) are disperse or inner phase(s), because the liquid droplets are finely distributed amongst the larger continuous phase droplets.[2] This type of emulsion is thermodynamically unstable, but can be stabilized for a period of time with applications of kinetic energy.[1] Surfactants (as the main emulsifiers) are used to reduce the interfacial tension between the two phases, and induce macroemulsion stability for a useful amount of time. Emulsions can be stabilized otherwise with polymers, solid particles (Pickering emulsions) or proteins.
Emulsion in which the particles of the dispersed phase have diameters from approximately 1 to 100 μm.
Note 1: Macro-emulsions comprise large droplets and thus are "unstable" in the sense that the droplets sediment or float, depending on the densities of the dispersed phase and dispersion medium. Separation of the dispersed and continuous phases usually occurs within time periods from a few seconds to a few hours, depending upon the viscosity of the fluid medium and the size and density of the droplets.
Note 2: Macro-emulsions usually contain low-molecular-weight or polymeric surfactants that decrease the rates of coalescence of dispersed droplets. Droplets of the dispersed phase may be also stabilized by adsorption of solid particles onto their surface (so-called Pickering stabilization).[3]
- ^ a b Shah, Dinesh O., ed. (1985). "Introduction to Macro- and Microemulsions". Macro- and microemulsions : theory and applications : based on a symposium sponsored by the Division of Industrial and Engineering Chemistry at the 186th Meeting of the American Chemical Society, Washington, D.C., August 28-September 2, 1983. ACS Symposium Series. Vol. 272. Washington, D.C.: American Chemical Society. pp. 1–13. doi:10.1021/bk-1985-0272.ch001. ISBN 978-0-8412-0896-4.
- ^ Butt, Hans-Jürgen; Graf, Karlheinz; Kappl, Michael (2006). Physics and chemistry of interfaces (2nd, rev. and enl. ed.). Weinheim: Wiley-VCH-Verl. pp. 108–109, 278–287. ISBN 978-3-527-40629-6.
- ^ Slomkowski, Stanislaw (2011). "Terminology of polymers and polymerization processes in dispersed systems (IUPAC Recommendations 2011)" (PDF). Pure and Applied Chemistry. 83 (12): 2229–2259. doi:10.1351/PAC-REC-10-06-03. S2CID 96812603.