Rheological properties of wormlike micelles in sodium oleate solution induced by sodium ion

Aqueous solutions of anionic surfactant, sodium oleate (NaOA), have been studied by means of steady-state shear theology and dynamic oscillatory technique. The micellar structure can be changed upon the addition of NaCl, Na2CO3 and NaCl/NaOH while NaOA concentration is maintained at 0.060 M. These systems except NaOA/NaCl show high viscosity and strong viscoelasticity. The hydroxide ion is very important for the formation of wormlike micelles. The anions of salts also have effect on the rheological properties of wormlike micelles. Three parameters: intersection frequency omega(i), plateau modulus G(0) and relaxation time T are also discussed. The Maxwell model and Cole-Cole plot are applied to investigate the dynamic viscoelasticity of wormlike micelles. Variation in surfactant packing parameter R-p can be used to explain the change of rheology and microstructure of the micelles. (c) 2007 Elsevier B.V. All rights reserved.