Coil Deformation, Scattering, and Fracture During Flow of Dilute Polymer Solutions

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9416955 Hoagland A "strong" flow field can substantially deform the usual coiled conformation of a long flexible polymer. This investigation will use laser light scattering to measure the molecular deformation of dilute polymer chains (MW10 million) dissolved in a flowing solvent. Experiments will focus on opposed jets and orifice flows, geometries where the flow field best approximates uniaxial elongation. Variables characterizing the chain, solvent, and flow strength will be adjusted systematically to test polymer/flow models from the literature. When flow-induced tension in the backbone becomes sufficiently large, the chain breaks, generating two fragment chains of potentially unequel molecular weight. The breadth of the fragment distribution reflects the chain conformation at the instant of fracture. Gel electrophoresis will be employed to examine the distributions produced in various steady and transient laminar flows capable of chain deformation and fracture. Turbulent drag reduction has often been explained using polymer/flow models that presuppose full chain extension; a study of chain fragments created in drag reducing flow will allow this hypothesis to be tested. %%% Flow-induced molecular deformation and chain fracture have been observed in nearly every application or environment where polymer solutions are found. A list of polymer technologies that would benefit from an improved understanding of polymer/flow interaction, and especially of flow-induced chain extension, includes the following: control and stabilization of bulk elongational flow properties (foods, coatings), filtration and processing in porous matrices (biopolymer manipulation, oil recovery), lubrication of sliding surfaces (memory devices, motor oils), and solution spinning (flow-induced crystallization of natural proteins, preparation of high modulus fibers).