LINEAR AND NON-LINEAR RHEOLOGY OF A WORMLIKE MICELLAR SYSTEM IN PRESENCE OF SODIUM TOSYLATE

In this experimental work, we investigate the influence of an organic counterion, sodium tosylate, on the rheological properties of an aqueo us solution of CTAB at the concentration of 0.05 M. With this system w e can clearly see shear thickening for small salt concentrations C-s a nd only shear thinning behavior at higher C-s characterized by a linea r evolution of eta=f(gamma) in a log-log representation. In these evol utions it is only in a very small domain of concentrations of the salt (near C-s=0.035 M) that we can observe a nearly constant plateau of t he shear stress against shear rate. The values of sigma(0) (characteri zing the stress plateau), G(0) (the plateau modulus) and tau(R) (the r elaxation time) obtained by dynamical rheological measurements, allow to compare experimental results obtained to predicted values of the th eory of Cates corresponding to the occurrence of shear induced banding structures.