RHEOLOGICAL PROPERTIES OF THE AQUEOUS MIXTURES OF CATIONIC-ANIONIC SURFACTANTS

The theological properties of the aqueous mixtures of cationic-anionic surfactants, both in single-phase systems and in aqueous two-phase systems, have been studied. Bizarre theological properties negative thixotropy, viscoelasticity and high viscosity of shear rate dependent at relatively low concentration - have been observed. An unusual viscosity change, that is, viscosity lowering with increasing concentration, was obtained. The negative thixotropy might be due to the existence of lamellar or sheet-like micelles, viscoelasticity might be induced by rodlike and lamellar or sheet-like micelles, the high viscosity might be a consequence of the formation of network by long rodlike micelles and the concentration-induced viscosity lowering could be interpreted in terms of the decrease of micellar dimensions with concentration.