Observation of polymer conformation hysteresis in extensional flow |
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Authors: | Schroeder Charles M Babcock Hazen P Shaqfeh Eric S G Chu Steven |
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Affiliation: | Department of Chemical Engineering, Stanford University, Stanford, CA 94305, USA. |
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Abstract: | Highly extensible Escherichia coli DNA molecules in planar extensional flow were visualized in dilute solution by fluorescence microscopy. For a narrow range of flow strengths, the molecules were found in either a coiled or highly extended conformation, depending on the deformation history of the polymer. This conformation hysteresis persists for many polymer relaxation times and is due to conformation-dependent hydrodynamic forces. Polymer conformational free-energy landscapes were calculated from computer simulations and show two free-energy minima for flow strengths near the coil-stretch transition. Hysteresis cycles may directly influence bulk-solution stresses and the development of stress-strain relations for dilute polymer flows. |
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