title: Influence of Surfactant Concentration and Counterion to Surfactant Ratio on Rheology of Wormlike Micelles.
abstract: The influence of concentration on rheological properties, including shear viscosity, shear instability, transient stress start-up and relaxation, apparent extensional viscosity, viscoelastic behavior, and microstructure by cryo-TEM, were studied with surfactant Ethoquad O/12, commercialized oleyl methyl bishydroxyethyl chloride, with counterion sodium salicylate. Counterion to surfactant molar ratios, xi, were 1.0 and 2.5. Concentrations for the xi=1 series are 5 mM/5 mM, 10 mM/10 mM, 50 mM/50 mM, 100 mM/100 mM, and 200 mM/200 mM (surfactant/counterion); those for the xi=2.5 series are 5 mM/12.5 mM, 10 mM/25 mM, 50 mM/125 mM, 100 mM/250 mM, and 200 mM/500 mM. The experimental results showed complicated rheological behavior with concentration changes. Shear viscosity decreases with increases in concentration for the xi=1 series. At xi=2.5 apparent viscosity increases with concentration above 10 mM. Viscoelasticity of the solutions also decreases with increases in surfactant concentration. At high concentration, a high shear rate is needed to induce viscoelasticity. A high extensional rate induces supermicellar structures. Gelation was observed during shear for the 100 mM/250 mM and 200 mM/500 mM solution in the cone-and-plate geometry. Cryo-TEM results revealed that all of the solutions examined had wormlike network micelle microstructures. Copyright 2001 Academic Press.
authors: Department of Chemical Engineering, The Ohio State University, Columbus, Ohio, 43210
authors: Zhiqing
authors: Z
authors: Lin
authors: Bin
authors: B
authors: Lu
authors: Jacques L.
authors: JL
authors: Zakin
authors: Yeshayahu
authors: Y
authors: Talmon
authors: Yi
authors: Y
authors: Zheng
authors: H. Ted
authors: HT
authors: Davis
authors: L. E.
authors: LE
authors: Scriven