Exploring the universal dynamics of dilute polymer solutions in extensional flows

A systematic framework introduced recently to obtain parameter-free predictions of material properties of dilute polymer solutions in extensional flows is reviewed. The essential constraint of ensuring that the model polymer molecule has a finite length is met by using a bead–spring chain model with finitely extensible springs, and the important microscopic phenomenon of excluded volume and hydrodynamic interactions are incorporated in the model. The key aspect of the scheme is the use of Brownian dynamics simulations in the context of a successive fine-graining procedure, which enables the consistent extrapolation of finite bead–spring chain data to the limit of a bead–rod model with the correct degree of flexibility and chain length. Predictions are shown to compare favourably with experimental observations of dilute solutions of polystyrene and DNA molecules.