Dresden 2006 – scientific programme
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CPP: Chemische Physik und Polymerphysik
CPP 1: Thin Films and Surfaces I
CPP 1.2: Talk
Monday, March 27, 2006, 10:00–10:15, ZEU Lich
Thin Film Rupture: From Elastic Fracture to Viscous Fingering — •Sylvain Gabriele1, Günter Reiter2, and Pascal Damman1 — 1Université de Mons Hainaut Laboratoire de PhysicoChimie des Polymères Place du Parc, 20 B-7000 Mons — 2Institut de Chimie des Surfaces Interfaces 15, rue Jean Starcky F-68057 Mulhouse
The stability of thin polymer films on top of a solid surface is of importance for numerous applications ranging from the lubrication to microlithographic resist films. When forced to cover a non-wettable substrate, thin liquid film could be unstable and dewet. We will focus on different geometries of dewetting (circular and planar) which exhibit a variety of artistic morphologies of instability. We report experimental observations that suggest that different viscoelastic instabilities are directly related to the dissipation mode: elastic or viscous. The first case of instability appears at the early stage of dewetting in the elastic regime and is related to stress dissipation by fracture propagation. The formation of cracks into the asymmetric rim can be interpreted as the instantaneous response of a circular dynamic elastic ring to an applied tangential stress. As a result, the fractures propagation forms a complex structure in a starry shape which provides a faster way to release the accumulated stress. After a characteristic time t2, rims show fluctuations in width and finally yield to an artistic finger-like pattern. The transversal instability of the rim is clearly reminiscent of the Rayleigh-Plateau instability. We argue that determining the onset of this rim instability represents a reliable way for measuring the disentanglement time of polymer which corresponds to the characteristic time t2.