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

Abstract

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 25ºC. The addition of tri(oxyethylene) nmonotetradecyl ether (C₁₄EO₃) to the semi-dilute aqueous solution of the LADLysine-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 (N_{o) increases with the} C₁₄EO₃ concentration gradually at first sharpl, and then finally decreases before phase separation.

Keywords: nonionic surfactant, wormlike micelles, rheology, viscoelastic solutions

DOI: 10.3126/jncs.v23i0.2098

J. Nepal Chem. Soc., Vol. 23, 2008/2009 Page: 65-73