Microrheology of giant-micelle solutions

Optical tracer-microrheology has been applied to study the rheological properties of a concentrated surfactant solution. Under the chosen conditions these surfactants self-assemble to form giant polymer-like micelles, resulting in a strongly viscoelastic liquid. A novel approach to the analysis of the local dynamic properties of tracer particles is presented, based on a combination of single- and multi-speckle diffusing wave spectroscopy (DWS). With this technique we could significantly extend the accessible frequency range to the key rheological properties as given by the loss and storage modulus, $G''(\omega)$ and $G'(\omega)$. A study of the high-frequency range, not accessible to standard techniques, shows good overall agreement with conventional models. However, we find a distinct temperature dependence of the characteristic modulus G0 incompatible with the simple picture of a single relaxation process.