Effect of Inorganic Salts on the Stability of W/O Emulsions Stabilized by 1-0-Alkylglycerol

Abstract

The water-in-oil (W/O) type emulsions composed of 1-0-alkylglycerol (GE), liquid paraffin and water became more viscous and stable when a certain amount of MgSO₄ was added. Since this emulsion system is considered to be stabilized by the liotropic liquid crystal of GE, the influence of addition of inorganic salts on the properties of the liquid crystal was investigated.
Though the liquid crystals of GE containing a certain amount of MgSO4 had a reversed hexagonal structure, as well as those without MgSO₄, the maximum water content was reduced with increasing MgSO₄ concentration. DSC measurement showed the addition of MgSO₄ made the interaction between GE and water smaller, and it consequently made th e hydrophilic portion of GE molecules more closely packed in the liquid crystals. As the result, the interplanar distance determined by small angle X-ray scattering decreased due to the contraction of the liquid crystals, and the dynamic elastisity became larger. Similar results were obtained with other inorganic salts.
Thus it is concluded the stabilization of W /O emulsions by the addition of inorganic salts is attributed to the enhancement of the rigidity of the interfacial layer constructed by the liquid crystals.