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Study of nano-emulsion formation by dilution of microemulsions.

Journal of colloid and interface science (2012-04-07)
I Solè, C Solans, A Maestro, C González, J M Gutiérrez
ABSTRACT

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 20 nm 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.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Dodecane, ReagentPlus®, ≥99%
Supelco
Density Standard 749 kg/m3, H&D Fitzgerald Ltd. Quality
Sigma-Aldrich
Dodecane, anhydrous, ≥99%
Supelco
Dodecane, analytical standard