title: Observation of polymer conformation hysteresis in extensional flow.
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.
authors.affiliation: Department of Chemical Engineering, Stanford University, Stanford, CA 94305, USA.
authors.forename: Charles M
authors.initials: CM
authors.lastname: Schroeder
authors.forename: Hazen P
authors.initials: HP
authors.lastname: Babcock
authors.forename: Eric S G
authors.initials: ES
authors.lastname: Shaqfeh
authors.forename: Steven
authors.initials: S
authors.lastname: Chu
mesh_terms: D001704:Biopolymers / Q000737:chemistry*; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D003198:Computer Simulation; D004269:DNA, Bacterial / Q000737:chemistry*; D004926:Escherichia coli; D008856:Microscopy, Fluorescence; D009690:Nucleic Acid Conformation; D013816:Thermodynamics
chemical_list: D001704:Biopolymers; D004269:DNA, Bacterial