A one-step process for oil-in-water-in-oil double emulsion formation using a single surfactant

A one-step double emulsification protocol using one surfactant was developed for oil-in-water-in-oil (O1/W/O2) double emulsions. Two n-alkane oils and three different surfactants were studied, with focus placed on a formulation containing mineral oil, glycerol monoleate (GMO) and deionized water. Phenomenologically, double emulsion formation and stability originate from the combined actions of phase inversion and interfacial charging of the oil/water interface during high shear homogenization. Based on the extent of double emulsion formation and stability, a critical emulsification zone dependent on the weight ratios of GMO to water was identified. Within this critical zone, enhanced O1/W/O2 emulsion formation occurred at higher pH and lower salt concentrations, demonstrating the key role of interfacial charging on double emulsification. Overall, this novel approach provides a novel platform for the development of double emulsions with simple compositions and processing requirements.

Graphical abstractFigure optionsDownload full-size imageDownload high-quality image (383 K)Download as PowerPoint slideHighlights► Oil-in-water-in-oil double emulsions (DEs) made with one surfactant using only one step. ► DE formation due to combination of phase inversion and interfacial charging of oil/water interface. ► Emulsification depends on surfactant/water ratio. ► Maximum DE formation at high pH and in absence of salt.