The structure of ultrathin Langmuir-Blodgett films of cadmium behenate.
Grazing incidence x-ray-diffraction investigations of the structures of Langmuir-Blodgett films of cadmium behenate with 1, 2, 3, 5, and 21 monolayers are reported. The single monolayer film, deposited on a hydrophilic substrate, showed a hexagonal structure, whereas the bilayer film, deposited on a hydrophobic substrate, had a rectangular structure with herringbone orientation of the acyl chains. With multilayer films formed on a hydrophilic substrate, it was possible to detect that the hexagonal structure of the first layer was retained when additional layers were deposited and that the additional layers had the same rectangular structure as the bilayer.
Application of off-specular scattering of X-rays and neutrons to the study of soft matter
Recent applications of the use of off-specular reflection of neutrons and X-rays in the study of soft matter are reviewed after a brief introduction to the status of the current theoretical treatment of such data. The review is intended to highlight the range of systems that may now be studied with off-specular reflection and recent progress in understanding the results that are observed. A few specific experimental cases are discussed as well as recent technical developments that may enable further more sophisticated treatments of off-specular scattering to be investigated.
Solvent-Induced Surface Morphology of Thin Polymer Films
With specular and off-specular X-ray scattering the surface morphology in terms of surface roughness, film quality, and roughness correlation in thin polymer films of polystyrene and fully brominated polystyrene is measured. During the preparation of the thin films on top of silicon substrates, the common solvent was varied. We investigated eight different solvents and three different solvent mixtures to depict the influence of typical solvent parameters. In the regime of a small solvent vapor pressure, we observed correlated roughness as the ultimate lower limit of accessible surface smoothness. The resulting films are homogeneous, and the surface roughness is given by the substrate. In an intermediate vapor pressure regime marked surface morphologies are detected, while at a high vapor pressure smoother films result again.