The Study of Salt Induced Viscoelastic Wormlike Micelles in Aqueous Systems of Mixed Anionic/Nonionic Surfactants

Formation of viscoelastic wormlike micelles in aqueous systems of mixed amino acid based anionic and nonionic surfactants in presence of salt is presented. N-dodecylglutamic acid (LAD) upon neutralization with L-Lysine in 1:2 mole ratio forms globular type of micelles above critical micelle concentration and the solution follows Newtonian fluid like behavior at 25°C. The addition of tri(oxyethylene) n-monotetradecyl ether (C14EO3) to the semi-dilute aqueous solution of the LAD-Lysine-2 induces one dimensional micellar growth and viscosity of solution increases. After a certain concentration of C14EO3 micelles get entangled and form a rigid network of wormlike micelles and viscosity increases by several orders of magnitude. The wormlike micellar solutions show a viscoelastic character and can be described the Maxwell mechanical model with a single stress relaxation. Rheological measurements have shown that zero shear viscosity (ηo) increases with the C14EO3 concentration gradually at first sharpl, and then finally decreases before phase separation