Self-thinning of dilute polydisperse polymer solution filament

In this paper, we study the combined effect of polydispersity and finite extensibility of macromolecules, as well as hydrodynamic interactions on capillary thinning of dilute polymer solutions using a molecular approach. Wide and narrow rectangular chain length distributions are considered. We study the temporal evolution of chain elongation parameters, filament radius, and elongation rate in both inertial-capillary (IC) and elasto-capillary (EC) regimes. In particular, we identify several types of chain-stretching behavior depending on chain length. It is shown that, following stretching in the IC regime, short chains return to an equilibrium coil state in the EC regime and are subsequently restretched during the final stage of filament thinning prior to breakup when the stretching rate increases sharply. We also show that as the distribution width increases, the time interval of the filament quasiexponential thinning in the EC regime increases as well. The obtained results help clarify the role of various factors in the experimentally observed exponential thinning of dilute polymer solutions. More generally, the proposed theory promise to be useful for understanding the role of polydispersity in the rheology of polymer solutions under extension.