Evidence of viscoelastic effects in highly concentrated aqueous solutions of the bile salt sodium deoxycholate by ultrasonic measurements

Abstract

Absorption (5–300 MHz and velocity (5–65 MHz) of ultrasound, density, and viscosity have been measured in highly concentrated aqueous solutions of sodium deoxycholate at 20 °C. Ultrasonic results show that classical viscous losses represent a large fraction of the experimental ones and that a small velocity dispersion is present. These experimental findings are interpreted on the grounds of a viscoelastic behavior of these solutions. Accordingly, the contributions from both volume and shear viscosity relaxation processes have been evaluated. For the former process a previously suggeted model of associated reactions is considered while the dynamic shear viscosity is related to the flexibility of the large micellar super aggregates.