Surfaces of Strongly Confined Polymer Thin Films Studied by X-Ray Scattering

The surfaces of thermally annealed thin polystyrene films on silicon were investigated by specular and diffuse x-ray scattering. The data cannot be interpreted satisfactorily with capillary wave calculations assuming attractive van der Waals substrate film interactions. The analysis shows that polystyrene films coated on silicon substrates are in a strongly confined state even for film thicknesses much larger than the radius of gyration, possibly due to strong confinement that arises from the interaction at the polymer/substrate interface and the viscoelastic behavior of the thin films