Eur. Phys. J. E (2009) 30: 75-81
https://doi.org/10.1140/epje/i2009-10509-4

Regular Article

Single flexible and semiflexible polymers at high shear: Non-monotonic and non-universal stretching response

Physik Department, Technische Universität München, 85748, Garching, Germany

^* e-mail: csendner@ph.tum.de

Received: 27 April 2009
Revised: 6 July 2009
Accepted: 20 August 2009
Published online: 24 September 2009

Abstract

Using Brownian hydrodynamic simulation techniques, we study single polymers in shear. We investigate the effects of hydrodynamic interactions, excluded volume, chain extensibility, chain length and semiflexibility. The well-known stretching behavior with increasing shear rate is only observed for low shear < , where is the shear rate at maximum polymer extension. For intermediate shear rates < < the radius of gyration decreases with increasing shear with minimum chain extension at . For even higher shear < the chain exhibits again shear stretching. This non-monotonic stretching behavior is obtained in the presence of excluded-volume and hydrodynamic interactions for sufficiently long and inextensible flexible polymers, while it is completely absent for Gaussian extensible chains. We establish the heuristic scaling laws ∼ N ^-1.4 and ∼ N ^0.7 as a function of chain length N , which implies that the regime of shear-induced chain compression widens with increasing chain length. These scaling laws also imply that the chain response at high shear rates is not a universal function of the Weissenberg number Wi = anymore, where is the equilibrium relaxation time. For semiflexible polymers a similar non-monotonic stretching response is obtained. By extrapolating the simulation results to lengths corresponding to experimentally studied DNA molecules, we find that the shear rate to reach the compression regime is experimentally realizable.