Dewetting of Polymer Films with Built-In Topographical Defects

Abstract

Polymer coatings in actual use are subject to wear and tear. In this experiment, we look into the dewetting instability of more realistic polymer coatings wherein topographical fluctuations pre-existed. The topographical defects, produced by rubbing the film surface with a piled fabric, could be varied for the density by changing the number of rubbings, N. First, the dewetting mechanism was determined by comparing the dewetting morphology between the unrubbed and rubbed films. Nucleation dewetting was ascribed to samples wherein the characteristic wave vector, q*, of the final dewetted morphology increased with increasing N, whereas spinodal dewetting was ascribed to samples wherein q* was affected little. Second, the evolution of dewetting was compared between the unrubbed and rubbed films. Our result shows that perturbations from rubbing do not produce changes in the free energy of the films that will alter the prevailing dewetting mechanism or the characteristic wave vector in spinodal dewetting. Nonetheless, the rubbing-induced defects do affect the rupturing process, in manners depending on the dominating dewetting mechanisms.