Rheological Properties of Anionic Surfactant Solutions in the Presence of Al3+ Counterion

Abstract

Aqueous solutions of ionic surfactants with strongly binding counterions exhibit wormlike or network properties. The properties of anionic micelles of sodium dodecyltrioxyethylene sulfate (AES) in the presence of multivalent counterion Al3+ were investigated by dynamic rheological methods. The steady-shear viscosity and stress, the zero-shear viscosity, the complex viscosity, and the dynamic shear modulus have been determined as a function of the surfactant and salt concentrations. Some interesting and noticeable results have been obtained, which can express the micellar growth and structure. The formation of wormlike micelles or network structure in surfactant solutions becomes much easier with increasing surfactant and salt concentrations. The Cox-Merz rule and the Cole-Cole plot are not applicable perfectly to the systems studied. The nonlinear viscoelasticity and non-Newtonian behavior can be found in all solutions according to the comparison with the simple Maxwell model. The technique of freeze-fracture transmission electron microscopy (FF-TEM) was also applied to confirm the formation of these interesting structures.