Coarse-graining intramolecular hydrodynamic interaction in dilute solutions of flexible polymers.

We present a scheme for coarse-graining hydrodynamic interactions in an isolated flexible homopolymer molecule in solution. In contrast to the conventional bead-spring model that employs spherical beads of fixed radii to represent the hydrodynamic characteristics of coarse-grained segments, we show that our procedure leads naturally to a discrete model of a polymer molecule as a chain of orientable and stretchable Gaussian blobs. This model accounts for both intrablob and interblob hydrodynamic interactions, which depend on the instantaneous shapes of the blobs. In Brownian dynamics simulations of initially stretched chains relaxing under quiescent conditions, the transient evolution of the mean-square end-to-end distance and first normal stress difference obtained with the Gaussian-blob model are found to be less sensitive to the degree of coarse graining, in comparison with the conventional bead-spring model with Rotne-Prager-Yamakawa hydrodynamic interactions.