Roles of chain stretch and concentration gradients in capillary thinning of polymer solutions

Abstract

Abstract Polymers inhibit the breakup of a liquid filament thinning under surface tension. The coupling of elasticity, capillarity and inertia leads to the well-known beads-on-a-string (BOAS) formation. Additionally, under different conditions, smaller satellite drops can form along the liquid bridge between the main beads. The development of BOAS and satellite drops is controlled by the rheology of the polymer solution. In this study, we consider the roles played by finite extensibility and anisotropic drag on the formation of satellite beads. In particular, we show that the more stretching a polymer chain can undergo, satellite beads are suppressed. The latter stages of capillary thinning has been shown to result in a phase separation resulting in what is referred to as a blistering pattern. We thus also conduct simulations of an inhomogeneous dilute polymer model that considers the competing effects of diffusion and stress gradients. We show that polymer is pulled axially towards the region connecting string and bead. This simple model does not predict a phase separation, but does reveal that pinchoff could be inhibited by the buildup of polymer concentration.