RHEOLOGICAL PROPERTIES OF SEMIDILUTE AND CONCENTRATED AQUEOUS-SOLUTIONS OF CETYLTRIMETHYLAMMONIUM BROMIDE IN THE PRESENCE OF POTASSIUM-BROMIDE

The frequency-dependent shear modulus of semidilute aqueous solutions of cetyltrimethylammonium bromide (CTAB) in the presence of 0.25 M KBr has been measured as a function of surfactant concentration and temperature. The comparison between the experimental data and the recent results of a computer simulation provides an estimate of tau(break), the time taken for a micelle of the mean length to break. In the moderately low concentration range, the values obtained for tau(break) from such an analysis are found to be in good agreement with those measured previously by means of a temperature-jump technique. At high concentration one observes an unexpected increase of tau(break) that is tentatively attributed to the fact that the micelles are likely to behave as stiff rods on the scale of the geometrical mesh-size of the entangled micellar network.