Hole formation and growth in freely standing polystyrene films

Using optical microscopy, we have measured the formation and growth of holes in freely standing polystyrene films in the melt state. For all films, we observed exponential growth of the hole radius and uniform thickening. Our measurements are interpreted in terms of the dependence of the viscosity on the shear strain rate associated with the hole growth process. The measurement of hole growth in thin freely standing polymer films provides a unique probe of nonlinear viscoelastic effects in confined polymers.