Langmuir, Vol.13, No.20, 5235-5243, 1997
Linear Viscoelasticity of Wormlike Micellar Solutions Found in the Vicinity of a Vesicle-Micelle Transition
Linear viscoelastic behavior of micellar solutions of cetyltrimethylammonium hydroxynaphthalene carboxylate is studied at temperatures above the vesicle-micelle transition under salt-free conditions and also in the presence of salt (sodium bromide and potassium acetate). The salt-free solutions, beyond a crossover volume fraction phi*, obey the micellar growth model of Mackintosh et al. The low values of phi* indicate that the effective charge on the micelles is very low. The decrease of the terminal relaxation time upon increasing surfactant concentration for volume fractions larger than similar to 6 phi* is attributed to the formation of intermicellar connections, favored by the diminution of the electrostatic contributions. A similar effect is found by the addition elf a salt that does not bind with the surfactant. The phase diagrams shown in this study suggest that the branched micelles constitute the inter mediate structures between linear micelles and bilayers.
Keywords:SURFACTANT MICELLES;DETERGENT MOLECULES;LIVING POLYMERS;AQUEOUS-MEDIA;POLYELECTROLYTE SOLUTIONS;DYNAMICS;SCATTERING;RELAXATION;REPTATION;NETWORK