Resonant soft x‐ray scattering and reflectivity study of the phase‐separated structure of thin poly(styrene‐b‐methyl methacrylate) films

Combined soft X‐ray scattering and reflectometry techniques promise analysis of polymer thin film domain structure and composition without resorting to chemical modification or isotopic labeling. This work explores the capabilities of these techniques in polymer films of poly(styrene‐b‐methyl methacrylate) (P(S‐b‐MMA)). The results demonstrate that the techniques give detailed information on the domain structure of thin films using well‐known modeling procedures. Discrepancies were noted between the X‐ray optical parameters that are needed to best fit the reflectivity data to the model and the expected parameters. The sources of these discrepancies are discussed in terms of instrument configuration parameters, sample attributes, and, particularly, anisotropy of the chromophore parameters. The results show that fitting the soft X‐ray reflectivity data is much more sensitive to these X‐ray optical parameters than the soft X‐ray scattering data. Nevertheless, fits to both types of data yield quantitative measures of the polymer film's lamellar morphology that are consistent with each other and with literature values. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013     

Highly Conductive Films of Layered Ternary Transition‐Metal Nitrides

Film studies : Epitaxial films of BaZrN₂ (see TEM image) and BaHfN₂ are grown by polymer‐assisted deposition on SrTiO₃ (STO) substrates. The films are phase‐pure, allowing the intrinsic physical properties of the ternary nitrides to be studied. From 5 to 300 K, the films exhibit metallic‐like resistivity–temperature behavior, with large residual resistivity ratios.

     

Real time evolution of liquid crystalline nanostructure during the digestion of formulation lipids using synchrotron small-angle X-ray scattering

The role of the digestion of lipids in facilitating absorption of poorly water-soluble compounds, such as vitamins, is not only an important nutritional issue but is increasingly being recognized as an important determinant in the effectiveness of lipid-based drug formulations. It has been known for some time that lipids often form complex liquid crystalline structures during digestion and that this may impact drug solubilization and absorption. However, until recently we have been unable to detect and characterize those structures in real time and have been limited in establishing the interplay between composition, digestion, and nanostructure. Here, we establish the use of an in vitro lipid digestion model used in conjunction with synchrotron small-angle X-ray scattering by first confirming its validity using known, nondigestible liquid crystalline systems, and then extend the model to study the real time evolution of nanostructure during the digestion of common formulation lipids. The formation of liquid crystalline structures from unstructured liquid formulations is discovered, and the kinetics of formation and dependence on composition is investigated.     

Electroreduction of diphenyldiazomethane in acetonitrile at a hanging mercury drop electrode

Cyclic voltammetric studies of the reduction of diphenyldiazomethane (Ph₂CN₂) in CH₃CN-Me₄NPF₆ at a hanging mercury drop electrode have established that the halflife of Ph₂CN₂^? is less than l ms at either 8°C or ?37°C.