Dispersion-Driven Morphology of Mechanically Confined Polymer Films

To probe the effects of mechanical confinement on freely standing polystyrene (PS) films, we have symmetrically capped freely standing PS films by thin, solid layers. Annealing of the trilayer films produces a novel lateral morphology which is driven by the dispersion force between the capping layers. A simple model is presented which describes the scaling behavior of the morphology with the layer thicknesses. The same morphology is observed for freely standing and supported films in eight different systems. We also demonstrate reversibility of the morphology by manipulation of the dispersion force.