Wednesday, September 5, 2012

1209.0163 (Ranganathan Prabhakar)

Enhancement of coil-stretch hysteresis by self-concentration in polymer
solutions
   [PDF]

Ranganathan Prabhakar
Coil-stretch hysteresis in extensional flows of dilute polymer solutions is shown to be strongly enhanced as concentration $c$ increases towards $c^\ast$, the critical overlap concentration. Large transverse fluctuations within the window of extension rates where hysteresis occurs cause greater intermolecular overlap between partially stretched molecules than at equilibrium. Hydrodynamic screening thus sets in at values of $c/c^\ast \ll 1$ for such chains, increasing their mean frictional coefficient and allowing for stretched states to be sustained at very low extension rates. Hysteresis progressively diminishes beyond $c^\ast$, and vanishes altogether when the crossover from Zimm to Rouse dynamics is complete. The concentration dependence of the width of the hysteresis window is thus non-monotonic, with a large maximum at $c/c^\ast = 1$.
View original: http://arxiv.org/abs/1209.0163

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