Study of nano-emulsion formation by dilution of microemulsions

• Published in: Journal of colloid and interface science Vol. 376; no. 1; pp. 133 - 139
• Main Authors: Solè, I., Solans, C., Maestro, A., González, C., Gutiérrez, J.M.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier Inc 15-06-2012; Elsevier
• Subjects: Alkanes - chemistry; Chemistry; Colloidal state and disperse state; Dilution of microemulsions; Dodecane; Droplets; Emulsification; Emulsions - chemistry; Emulsions. Microemulsions. Foams; Exact sciences and technology; General and physical chemistry; Hexanols - chemistry; Low-energy methods; Microemulsions; Nano-emulsions; Nanocomposites; Nanoemulsions; Nanomaterials; Nanostructure; Oils - chemistry; Pentanols - chemistry; Self-emulsification; Sodium Dodecyl Sulfate - chemistry; Stability; Surface-Active Agents - chemistry; Water - chemistry; Dilution of microemulsions; Low-energy methods; Microemulsions; Nano-emulsions; Self-emulsification; Water; Composition; Stability; Dodecane; Emulsification; Alcohol; Cosurfactant; Droplet; Ionic surfactant; Equilibrium; Lauryl sulfate; Anionic surfactant; Dilution; Emulsion; Oil; Energy; Models; Microemulsion; Diameter
• ISSN: 0021-9797; 1095-7103
• DOI: 10.1016/j.jcis.2012.02.063

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► Effect of dilution procedure and cosurfactant nature on O/W nano-emulsion formation by self-emulsification. ► Dilution of O/W microemulsions results in nano-emulsions regardless the dilution procedure. ► Dilution of W/O microemulsions only results in nano-emulsions when water is added stepwise. ► Nano-emulsion size decreases with cosurfactant alkyl chain length. ► Nano-emulsion stability increases with cosurfactant alkyl chain length.
The influence of different dilution procedures on the properties of oil-in-water (O/W) nano-emulsions obtained by dilution of oil-in-water (O/W) and water-in-oil (W/O) microemulsions has been studied. The system water/SDS/cosurfactant/dodecane with either hexanol or pentanol as cosurfactant was chosen as model system. The dilution procedures consisted of adding water (or microemulsion) stepwise or at once over a microemulsion (or water). Starting emulsification from O/W microemulsions, nano-emulsions with droplet diameters of 20nm are obtained, independently on the microemulsion composition and the dilution procedure used. In contrast, starting emulsification from W/O microemulsions, nano-emulsions are only obtained if the emulsification conditions allow reaching the equilibrium in an O/W microemulsion domain during the process. These conditions are achieved by stepwise addition of water over W/O microemulsions with O/S ratios at which a direct microemulsion domain is crossed during emulsification. The nature of the alcohol used as cosurfactant has been found to play a key role on the properties of the nano-emulsions obtained: nano-emulsions in the system using hexanol as cosurfactant are smaller in size, lower in polydispersity, and have a higher stability than those with pentanol.