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 G(0) incompatible with the simple picture of a single relaxation process.