Influence of outer-layer finite-size effects on the rupture kinetics of a thin polymer film embedded in an immiscible matrix

TL;DR

This study models the rupture kinetics of thin polymer films in multilayer systems, highlighting the significant role of boundary conditions and showing that finite-size effects are not necessary to explain the observed dynamics.

Contribution

It provides a scaling model that accurately describes hole growth in thin films considering no-slip boundaries, without requiring finite-size effects.

Findings

Thinner films rupture faster than thicker ones.

The experimental data collapse onto a single master curve.

Model predictions agree with observed hole growth dynamics.

Abstract

In capillary-driven fluid dynamics, simple departures from equilibrium offer the chance to quantitatively model the resulting relaxations. These dynamics in turn provide insight on both practical and fundamental aspects of thin-film hydrodynamics. In this work, we describe a model trilayer dewetting experiment elucidating the effect of solid, no-slip confining boundaries on the bursting of a liquid film in a viscous environment. This experiment was inspired by an industrial polymer processing technique, multilayer coextrusion, in which thousands of alternating layers are stacked atop one another. When pushed to the nanoscale limit, the individual layers are found to break up on time scales shorter than the processing time. To gain insight on this dynamic problem, we here directly observe the growth rate of holes in the middle layer of the trilayer films described above, wherein the distance between the inner film and solid boundary can be orders of magnitude larger than its thickness. In otherwise identical experimental conditions, thinner films break up faster than thicker ones. This observation is found to agree with a scaling model that balances capillary driving power and viscous dissipation with, crucially, a no-slip boundary condition at the solid substrate/viscous environment boundary. In particular, even for the thinnest middle-layers, no finite-size effect is needed to explain the data. The dynamics of hole growth is captured by a single master curve over four orders of magnitude in the dimensionless hole radius and time, and is found to agree well with predictions including analytic expressions for the dissipation.