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Seminars
Rheological Observation of Glassy Dynamics of Dilute Plymer Solutions near the Coil-Stretch Transition in Elongational Flows
Professor J. Ravi Prakash
Department of Chemical Engineering
Monash University, Melbourne, Australia
When: Thursday, January 11, 2007
Time: 2:30 PM to 3:30 PM
Where: 1070 Duncan Hall
Abstract:
The macroscopic dynamics of dilute polymer solutions have long been conjectured to exhibit a glass-like slowdown caused by ergodicity breaking, in the vicinity of the coil-stretch transition in elongational flows. In this seminar, I report experimental observations using a filament stretching rheometer that confirms the existence of such glassy states. It is observed that different time-dependent elongational
strain rate profiles lead to pronounced history-dependence and aging effects within a narrow range of strain rates. Computer simulations are shown to reproduce the experimental observations, and indicate that the origin of the deformation history dependence lies in the conformation dependence of hydrodynamic forces. The results have a direct bearing on the analysis and design of processes employing dilute polymer solutions, such as ink-jet printing, surface coating, and turbulent-drag reduction.
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