Dynamics of Complex Polymer Fluids During Flow & Processing
Wesley R. Burghardt
Departments of Chemical and Biological Engineering and
Materials Science and Engineering
The non-Newtonian flow characteristics of polymers and other complex fluids is intimately related to the ability of applied flow fields to significantly perturb the molecular or meso-scale structure. Consequently, modern research strongly emphasizes understanding of the molecular or microstructural origins of complex rheological behavior. At the same time, technological applications of polymers often rely on flow-induced structural changes (i.e. molecular orientation) which profoundly affect the resulting material properties. This talk will provide a survey of our efforts at the Advanced Photon Source to establish in situ x-ray scattering methods as a tool to directly probe the structure of complex polymer fluids during flow and processing. The combination of high flux with fast area detectors now enables real-time studies of transient structural dynamics, which can, in many cases, be directly linked to the macroscopic rheological behavior. In addition, high energy (short wavelength) x-rays allow new experimental concepts which extend the scope of possible studies. The presentation will survey available instrumentation ranging from shear cells for fundamental studies in simple flows, to in situ studies during processing via extrusion or injection molding. Applications of these methods will be drawn from diverse examples of complex polymer fluids, including nematic liquid crystalline polymers, lamellar block copolymers, bicontinuous polymer microemulsions and polymer-clay nanocomposites.