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

The effect of concentration on coil-stretch hysteresis in extensional flows of polymer solutions is examined with insights from Brownian dynamics simulations of isolated chains and scaling theory for non-dilute solutions. In the hysteresis regime, stretched molecules pervade larger volumes than equilibrium coils. For such chains, intermolecular overlap and hydrodynamic screening crossover set in at concentrations much smaller than the critical overlap concentration $c^\ast$ for equilibrium coils. The width of the hysteresis window is consequently strongly enhanced around $c^\ast$.