On the mechanics of rim instabilities in viscoelastic polymer thin films

Abstract

Dewetting of polystyrene thin films deposited onto nonwettable silicon wafers displays unusual dynamics and various morphologies. These instability patterns have been shown to be either discrete circular holes or surface undulations, in the case of nucleated dewetting or spinodal decomposition repectively. Here, we present the existence of a new rim instability, only effective in the elasticity dominated regime, leading to the propagation of fractures into the rim. The comparison with the viscous fingering instability suggests that, in addition to dewetting dynamics, the study of elasticity and viscous-dominated rim instabilities may lead to improved understanding of the influence of viscoelasticity, slippage and friction at the film/substrate interface.