Effects of some anions of the Hofmeister series on the rheology of cetyltrimethylammonium-salicylate wormlike micelles

The linear viscoelasticity of systems formed with cetyltrimetylammonium salicylate (CTASal) was investigated. This system is interesting because this complex salt forms wormlike micelles (WLM), in which the aromatic ring of salicylate threads into the micelle palisade. The chains of WLM of CTASal have excess of positive charge and, in the semi-dilute regime, form systems with very long relaxation time. However, the relaxation time become short when salt is added. The effect of NaCl, NaBr, NaNO3, NaSCN and NaSalicylate, on CTASal solutions was investigated by using rheology and SAXS. The systems in the presence of salts present shorter relaxation times due to the charge neutralization associated with the adsorption of the anions on the micelles surface. The magnitude of the effect depends on the nature of the anions, which follows the Hofmeister series. (C) 2015 Elsevier B.V. All rights reserved.