Concentration-induced micelle-to-vesicle transitions in aqueous sodium ricinate branched polyoxyethylene ether solutions

The aggregation behavior of a novel carboxylate surfactant, sodium ricinate branched polyoxyethylene ether, was studied by dynamic light scattering (DLS), ultraviolet visible spectrophotometer, and transmission electron microscope (TEM) measurements. Concentration-induced micelle-to-vesicle transitions were observed when the concentration of the surfactant solution was higher than 0.1 mmol/L. And the size of the vesicles decreased with increase of the concentration of surfactant. We performed a detailed study on this interesting phenomenon and proposed a possible mechanism: intermolecular hydrogen bonds of branched polyoxyethylene ether in the molecule may be the reasons that lead to the formation of vesicles in aqueous solutions of sodium ricinate branched polyoxyethylene ether.