Capillary-driven thinning of a dilute bidisperse polymer solution

This paper examines capillary thinning of dilute monodisperse and bidisperse polymer solutions using a molecular approach and taking into account the finite extensibility (FE) of macromolecules and hydrodynamic interactions. The equations of chain stretching dynamics were used to study their time evolution at intermediate and high stretching degrees, as well as the behavior of the filament radius and the stretching rate. It is shown that in a bidisperse solution, long and short chains experience non-monotonic stretching in the elasto-capillary (EC) regime. This leads to the development of a maximum in the time-dependence of the stretching rate when the fraction of long chains is small. When the fraction of long chains exceeds some critical value, short chains relax to an equilibrium coiled state upon passing from the inertio-capillary regime to the EC regime, and then these chains stretch again. A physical explanation for this behavior is proposed.