Phase and rheological behavior of the hexadecyl(trimethyl)azanium; 2-hydroxybenzoate/water system.

The phase and rheological behavior of hexadecyl(trimethyl)azanium; 2-hydroxybenzoate (CTAS), and water as a function of surfactant concentration and temperature are investigated here. The critical micellization concentration (cmc1) and the concentration at which the structure of aggregates changes (cmc2) as well as the Krafft temperature (TK) are reported. A large micellar solution region exhibiting high viscosity, as well as hexagonal- and lamellar-phase regions were identified. In the dilute region, below the overlapping entanglement concentration (C∗), the micellar solutions exhibit shear thickening. Above C∗, wormlike micelles form and the solutions show strong viscoelasticity with Maxwell behavior in the linear regime and shear banding flow in the non-linear regime.