Charge screening effects on filament dynamics in xanthan gum solutions

We experimentally investigate the filament dynamics of non-Newtonian drops falling under gravity through air, and report the effects of semiilute concentrations of the polyelectrolyte polymer xanthan gum mixed in 80:20 glycerol/water with varying concentrations of potassium chloride KCl). We find that the addition of 780 ppm xanthan gum to the glycerol/water solvent dramatically increases the drop length just before pinch-off, y two orders of magnitude. This length is decreased by as much as an order of magnitude with the addition of KCl. The qualitative dynamics f bead formation on the filament is also very sensitive to added salt. These experimental observations are related to well-known changes in the olecular structure of xanthan gum due to charge screening effects. 2006 Elsevier B.V. All rights reserved.