Molecular configurations in a droplet detachment process of a complex liquid

We studied the microscopic polymer conformations in the droplet detachment process of an elastic semi-dilute polyelectrolytic Xanthan solution by measuring the instantaneous birefringence. As in earlier studies, we observe the suppression of the finite time singularity of the pinch-off process and the occurrence of an elastic filament. Our microscopic measurements reveal that the relatively stiff Xanthan molecules are already significantly pre-stretched to about 90 % of their final extension at the moment the filament appears. At later stages of the detachment process, we find evidence of a concentration enhancement due to the elongational flow.