Large-scale and local-scale structures in polymer-blend films: a grazing-incidence ultra-small-angle X-ray scattering and sub-microbeam grazing-incidence small-angle X-ray scattering investigation

Phase-separation structures are installed by solution casting and flow of a binary polymer-blend solution of polystyrene and poly-n-butylacrylate in toluene on silicon. Optical microscopy and scanning-probe microscopy measurements provide the surface topography. Large-scale structures are probed with high-resolution or grazing-incidence ultra-small-angle X-ray scattering enabled by high reciprocal-space resolution. Correspondingly, structures of up to 13 µm are resolved. Local-scale structures are detected with sub-microbeam grazing-incidence small-angle X-ray scattering, providing a high real-space resolution of 1 µm. Nanometre-size cavities are found in the polystyrene-rich parts of the blend film.