Disentanglement in ultrathin polymer films, surface strain, and auto-dewetting

In this paper, we emphasize the importance of the film preparation on the mechanical properties of polymer thin films. With shear and adhesion measurements, conducted with scanning force microscopy (SFM), we discuss the effect of spin casting on the degree of disentanglement of polymer chains in the boundary regime to the substrate surface. The thickness of the mechanically strained boundary layer is measured, and its unexpected far-field effect discussed with a two-fluid model. The surface interaction and mechanical properties, which were obtained from unannealed polyethylene copropylene (PEP) films, are compared to annealed PEP films and to auto-dewetting occurrences in strained systems. The measurements show that spin coating together with the interaction strength of the substrate surface can cause autophobicity.