Dewetting of Thin Viscoelastic Polymer Films on Slippery Substrates

TL;DR

This paper develops a theoretical model for the dewetting behavior of thin viscoelastic polymer films on slippery substrates, explaining asymmetric rim shapes and velocity decay, and accounts for experimental observations of rapid velocity decrease due to residual stresses.

Contribution

It introduces a new theoretical approach incorporating viscoelasticity and slippage to explain dewetting dynamics and morphologies of thin polymer films.

Findings

Asymmetric rim shapes during dewetting.

Dewetting velocity decreases as t^{-1/2} for short times.

Residual stresses explain faster velocity decay in experiments.

Abstract

Dewetting of thin polystyrene films deposited onto silicone wafers at temperatures close to the glass transition exhibits unusual dynamics and front morphologies. Here, we present a new theoretical approach of these phenomena taking into account both the viscoelastic properties of the film and the non-zero velocity of the film at the interface with the substrate (due to slippage). We then show how these two ingredients lead to : (a) A very asymmetric shape of the rim as the film dewetts, (b) A decrease of the dewetting velocity with time like $t^{-{1/2}}$ for times shorter than the reptation time (for larger times, the dewetting velocity reaches a constant value). Very recent experiments by Damman, Baudelet and Reiter [Phys. Rev. Lett. {\bf 91}, 216101 (2003)] present, however, a much faster decrease of the dewetting velocity. We then show how this striking result can be explained by the presence of residual stresses in the film.