Rheological Properties of Viscoelastic Solutions in a Cationic Surfactant-Organic Salts-Water System

Viscoelastic solutions formed in the mixed aqueous solutions of 3-tetradecyloxy-2-hydroxypropyltrimethylammonium bromide (R(14)HTAB) and aromatic salts such as sodium salicylate (NaSal), sodium 1-hydroxynaphthalene-2-carboxylate (1SHNC), and sodium 2-hydroxynaphthalene-3-carboxylate (2SHNC) were systematically studied by steady and dynamic shear rheology in terms of concentration and temperature. In the absence of a salt, R(14)HTAB only produced spherical or short cylindrical micelles within a range of concentrations of 100-400 mmol kg(-1). The addition of aromatic salts induced one-dimensional growth of micelles generating wormlike micelles. Zero-shear viscosity of the solutions shows viscosity maxima behavior in the examined range of salt concentration, where the strongest and the most stable network structures were formed. The changes in the viscoelastic behavior are a result of variation of the structural relaxation time, indicating that the flow behavior is primarily controlled by micellar kinetics. The microstructure of wormlike micelles and the reason for the variation in the microstructure with an increase in the additive concentration has been analyzed by infrared and H-1 NMR spectra measurements. The zero-shear viscosity reduces exponentially with increasing temperature.