Effects of stiffness on the flow behavior of polymers

A recent model of the behavior of Gaussian chains in steady shear flow [J. Chem. Phys. 112, 8707 (2000)] is extended to include the effects of stiffne ss and finite extensibility. Calculations of the shear rate dependence of f ractional elongation and of the time dependence of size fluctuations are fo und to be in good agreement with results from an experimental study of the behavior of single chains of DNA in steady shear flow. As in the earlier ap proach to the polymer-flow problem, we have ignored excluded volume and hyd rodynamic interactions, but have instead added a bending energy contributio n to the Hamiltonian of the chain, and have treated the usual connectivity term as a contribution to chain stretching that can be adjusted to ensure t hat the average size of the chain is fixed. The inclusion of stiffness and finite extensibility in the present treatment is found to produce significa nt improvements over the approach based purely on flexible chains. (C) 2000 American Institute of Physics. [S0021-9606(00)50747-8].