Birefringence and Light-Scattering Studies of Concentrated Polymer Solutions in Strong Flows

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This research deals with an experimental and theoretical study of concentrated polymer solutions in strong flows. The objective is a better understanding of the changes in polymer conformation which occur as a consequence of the flow, and conversely, the modifications of the flow which occur because of the polymer. The proposed experimental measurements utilize a two-color birefringence system to provide real-time data on polymer conformation in transient conditions, and dynamic light scattering to obtain local, instantaneous data on the velocity gradient in the flow. From a fundamental point of view, the concern is with the relationship between molecular parameters, particularly the molecular weight and molecular-weight distribution, on polymer relaxation phenomena in the so-called "viscoelastic" regime of large deformation from the equilibrium state. In a more general sense, the research deals with the effects of various kinds if flow on polymer conformation, and with the implications for polymer processing, including the potential for manipulation of macroscopic properties of polymeric materials through flow-induced modifications of conformation.