Regensburg 2007 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 12: Polymer Physics III: Interfaces

CPP 12.8: Vortrag

Dienstag, 27. März 2007, 12:00–12:15, H40

New observations during onset and final stages of capillary-breakup experiments on semidilute polymer solutions — •Rainer Sattler and Christian Wagner — Universität des Saarlandes, Geb. E2 6 3.OG, Postfach 151150, 66041 Saarbrücken

We investigate the droplet-pinching and capillary-breakup of polymer solutions using high speed video microscopy. Recent experiments on semidilute solutions of Polyethylene Oxide were performed to examine the nature and prerequisites for the supposedly iterative formation of beads on the thinning filament, which form as the extension of the polymers saturates.

There are clear indications for concentration enhancement during the formation of the different generations of beads not taken into consideration in existing models. Special emphasis is put on the discussion which mechanisms control the onset of the instability. We found indirect evidence showing that besides inertial effects modes of capillary waves at amplitudes below the resolution of optical microscopy cause dramatic deviations from expectations assuming a simple extensional flow during the thinning of the capillary bridge.

The presented experimental results can contribute to a better understanding of the growth of these instabilities and the behaviour of polymers in extensional flow relevant for technical and biological processes as well as giving reason for enhancements in theoretical description.