Scattering properties of salt-free wormlike micellar solutions

Abstract

Static and dynamic light scattering and conductivity experiments were carried out on salt-free aqueous micellar solutions of cetyltrimethylammonium n-hexane sulfonate (CTAC6SO3) and cetyltrimethylammonium n-heptane sulfonate (CTAC7SO3) as a function of surfactant concentration. This study confirms the analogy between the behavior in the semi-dilute regime of elongated micellar systems and "classical" polyelectrolyte solutions. Time-resolved scattering experiments performed after a variation of concentration from about twice the overlap volume fraction Φ * to less than half of it revealed the existence of a structural relaxation with a characteristic time of several hours. PACS. 36.20.-r Macromolecules and polymer molecules -61.25.Hq Macromolecular and polymer solutions; polymer melts; swelling -82.70.-y Disperse systems

Ring-driven shear thickening in wormlike micelles?

“…Importantly, recent work shows that much of the slow relaxation behavior observed in response to rheological disturbances can be reproduced by studying temperature changes (or even concentration changes [19]) instead [18]. This confirms that some important timescales for rheology stem directly from the micellar kinetics in the quiescent state, as probed in T -jump (or sudden dilution).…”

Shear thickening in dilute solutions of wormlike micelles

“…We will consider the range 0.9 < f < 0.95. The lower limit is given by the Manning calculation [30] and the upper one comes from light scattering measurements [31].…”

Rheology of Wormlike Micelles: Equilibrium Properties and Shear Banding Transitions

“…This may have considerable effects on the stability and equilibrium properties of the phases [185,186]. However, in the concentrated regime, the ionic strength is always large (of the order of 1 M) and electrostatics has a minor effect.…”

“…Diluting micellar phases (and keeping the solutions free of additional salt) increases the range of the electrostatic interaction between micelles. This may have considerable effects on the stability and equilibrium properties of the phases, as it was recently pointed out [185,186]. In the concentrated regime on the contrary, the ionic strength is always large (of the order of 1 M) and electrostatics has a minor effect.…”