PROJECT SUMMARY Complex fluids, which are solutions containing surfactants, polymers, colloids or a combination of these components, are ubiquitous throughout the chemical and materials processing and biotechnology industries. These fluids often display unusual dynamical properties, typically probed by mechanical rheometry. However, since the shearing forces induced by a mechanical rheometer can lead to gross structural changes, techniques are lacking to probe biologically and industrially relevant complex fluids in their quiescent state. Optical techniques offer a noninvasite, accurate approach to fill this void. The objective is to construct a diffusing wave spectrometer (DWS) for performing these quiescent measurements. The experiments will focus on five model systems in the initial studies to be conducted with this instrumentation. These systems include: (1) wormlike surfactant micelles or 'living' polymers with an eye towards investigating their high frequency dynamical properties; (2) polymer gels and (3) solutions with the goal of establishing a means of determining the relaxation time spectrum and the effective mesh size, each of which have great implications for separations applications (i.e. electrophoresis); (4) colloidal dispersions, especially the onset of glassy behavior, and (5) actin filament networks where our interest lies toward determining the validity of mechanical rheometry measurements of such systems and whether our optical technique is capable of resolving biologically important dynamical processes which may also occur in vivo.
