Dewetting of thin polymer films: Influence of interface evolution

TL;DR

This paper investigates how the evolution of interface properties, like friction or slip length, influences the dewetting behavior of ultrathin polymer films, revealing that interface dynamics can be inferred from dewetting patterns.

Contribution

It introduces a model linking interface evolution, specifically friction and slip length changes, to dewetting dynamics, highlighting the role of interface aging in thin polymer films.

Findings

Maximum rim width can be caused by evolving friction or slip length.

Sample age influences the dewetting behavior and rim formation.

Interface evolution can be used to measure polymer-polymer interface aging.

Abstract

The dewetting dynamics of ultrathin polymer films, e.g. in the model system of polystyrene on a polydimethylsiloxane-covered substrate, exhibits interesting behavior like a fast decay of the dewetting velocity and a maximum in the width of the built-up rim in the course of time. These features have been recently ascribed to the relaxation of residual stresses in the film that stem from the nonequilibrium preparation of the samples. Recent experiments by Coppee et al. on PS with low molecular weight, where such stresses could not be evidenced, showed however similar behavior. By scaling arguments and numerical solution of a thin film viscoelastic model we show that the maximum in the width of the rim can be caused by a temporal evolution of the friction coefficient (or equivalently of the slip length), for which we discuss two possible mechanisms. In addition, the maximum in the width is affected by the sample age. As a consequence, knowing the temporal behavior of friction (or slip length) in principle allows to measure the aging dynamics of a polymer-polymer interface by simple dewetting experiments.