An alternative to the bead-rod model: Bead-spring chains with successive fine graining

Abstract

Brownian dynamics simulations are carried out to compare the predictions of a bead-spring chain model with the bead-rod model and a model with stiff FENE–Fraenkel springs. The successive fine graining (SFG) scheme is used to extrapolate the results of bead-spring chain simulations to the limit where the number of springs ( N s ) approaches the number of rods (equal to the number of Kuhn steps, N k ) in a bead-rod model. It is found that in the absence of excluded volume (EV) and hydrodynamic interactions (HI), the analytical results for linear viscoelastic properties obtained using the bead-spring model with the SFG scheme are in complete agreement with the infinitely stiff Fraenkel spring results. The numerical computations of linear viscoelastic properties in the presence of HI are found to be in good agreement with the results of the bead-rod model. In shear flow, the SFG results show excellent agreement with bead-rod results for a range of shear rates both in the absence and presence of HI and EV. In the limit N s → N k , the numerical and analytical results obtained using the SFG scheme are found to be independent of the choice of spring force law.