Dewetting dynamics of stressed viscoelastic thin polymer films

TL;DR

This paper investigates how residual stresses influence the dewetting behavior of ultrathin viscoelastic polymer films, revealing complex dynamics and dissipation mechanisms that explain experimental observations.

Contribution

It introduces a viscoelastic thin film model accounting for residual stresses, providing new insights into dewetting dynamics and rim formation in stressed polymer films.

Findings

Profiles and dissipation mechanisms evolve during dewetting.

Nonlinear friction affects the dominance of dissipation modes.

Explains the maximum rim width observed experimentally.

Abstract

Ultrathin polymer films that are produced e.g. by spin-coating are believed to be stressed since polymers are 'frozen in' into out-of-equilibrium configurations during this process. In the framework of a viscoelastic thin film model, we study the effects of lateral residual stresses on the dewetting dynamics of the film. The temporal evolution of the height profiles and the velocity profiles inside the film as well as the dissipation mechanisms are investigated in detail. Both the shape of the profiles and the importance of frictional dissipation vs. viscous dissipation inside the film are found to change in the course of dewetting. The interplay of the non-stationary profiles, the relaxing initial stress and changes in the dominance of the two dissipation mechanisms caused by nonlinear friction with the substrate is responsible for the rich behavior of the system. In particular, our analysis sheds new light on the occurrence of the unexpected maximum in the rim width obtained recently in experiments on PS-PDMS systems.