Coarse-graining of hydrodynamic and excluded volume interactions in polymer chains

R, Prabhakar, E. M. Sevick, D. R. M. Williams
Australian National University

Conventional bead-spring models of linear polymers incorporating hydrodynamic and/ or excluded volume interactions assume that the coarse-grained polymer segments represented as springs are essentially isotropic i.e. the beads are always spherical. While this approach works well for static and dynamic properties of long, flexible molecules near equilibrium, in situations where molecules are likely to be stretched out, spherical beads with fixed constant friction and excluded-volume parameters cannot accurately represent interactions between elongated segments. We treat polymer segments as diffuse axissymetric ellipsoids to derive expressions for the configuration-dependent mobility matrix and excluded-volume potential which account for the effects of segmental anisotropy and orientation on inter-segmental interactions. Brownian dynamics simulations' results for static and dynamics properties obtained with coarse representations of flexible and semiflexible chains are compared with results obtained with finer   representations using conventional bead-spring chains.