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CPP: Chemische Physik und Polymerphysik
CPP 23: Polymer films I
CPP 23.4: Talk
Tuesday, March 8, 2005, 14:45–15:00, TU C130
Is fluid dynamics of thin polymer films dominated by thermal noise? — •Klaus Mecke1,2, Renate Konrad3, and Markus Rauscher2 — 1Institut für theoretische Physik, Universität Erlangen-Nürnberg, Staudtstrasse 7, D-91058 Erlangen — 2MPI für Metallforschung, Stuttgart — 3Experimentalphysik, Universität Saarbrücken
In bulk fluids hydrodynamic Navier-Stokes equations are proven to be valid down to nanometer scales. However, during dewetting processes of thin liquid films of nanometer thickness the interplay of substrate potential and thermal noise can lead to qualitative different behavior on laterally much larger scales up to microns. By deriving a stochastic thin film equation with a conserved noise term we show that, e.g. the spectrum of capillary waves change due to thermal fluctuations from an exponential decay to a power law for large wavevectors. Also the time evolution of film roughness σ(t) and of the typical wavelength λ(t) of unstable perturbations change qualitatively. Whereas a deterministic Navier-Stokes equation in lubrication approximation predicts in the linear regime a constant λ(t) and even an initial decay of σ(t), thermal noise leads to a much faster increase of roughness and λ(t), i.e. to coarsening. These findings are robust, i.e., the predicted breakdown of the deterministic hydrodynamic description of thin liquid films on a nanometer scale occurs for small thermal noise amplitudes and for a large class of substrate interactions. The theoretical predictions seem to be confirmed in recent AFM measurements of dewetting of thin polymer films.