Viscoelastic behavior of water/AOT/n-heptane microemulsions by ultrasonic absorption investigation

The ultrasonic absorption in water/sodium bis(2-ethylhexyl) sulfosuccinate (AOT)/n-heptane system has been measured at 25 °C, as a function of the water/AOT molar ratio (X) and of the volume fraction (φ) of the micellar phase. The ultrasonic spectra have been found strongly dependent on φ and nearly independent on X. In particular, as φ increases, ultrasonic dynamics shifts from a single to a distribution of relaxation times with occurrence of viscoelastic effects. Such findings have been correlated to the increased connectivity of the micellar network.