LINEAR VISCOELASTICITY OF WORMLIKE MICELLAR SOLUTIONS FOUND IN THE VICINITY OF A VESICLE-MICELLE TRANSITION

Linear viscoelastic behavior of micellar solutions of cetyltrimethylam monium 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 mic ellar growth model of Mackintosh et al. The low values of phi indicat e that the effective charge on the micelles is very low. The decrease of the terminal relaxation time upon increasing surfactant concentrati on 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 consti tute the inter mediate structures between linear micelles and bilayers .