Self-assembly and emulsions of oleic acid-oleate mixtures in glycerol

It is known that mixtures of oleic acid and sodium oleate spontaneously form vesicles in water. In this paper, we study this system in glycerol, and show that it also forms vesicles in this solvent, but with a considerably lower diameter. The critical vesicle concentration (cvc) was higher in glycerol (cvc = 27.1 mM) than in water (cvc = 0.10 mM). This finding was confirmed using an analogous system made of palmitoleic acid and palmitoleate. The vesicles in glycerol were characterized using small-angle neutron scattering (SANS) which showed that the fatty acids are embedded in a fluid bilayer phase. These fatty acid dispersions were used to produce emulsions in glycerol, using hexadecane as the oil component. We show that a higher energy is required to produce emulsions in glycerol than in water, probably because of the higher viscosity of glycerol. However, emulsions were shown to be stable in glycerol. Altogether, this shows that supramolecular self-assembly occurs in glycerol, and that emulsions can be successfully produced in this solvent.