A. S. Orekhov

Study of polyelectrolyte complexes of chitosan and sulfoethyl cellulose

The complexing of polycation chitosan and polyanion sulphoethyl cellulose during the formation of polyelectrolyte simplex membranes using the layer-by-layer deposition of a solution of one polyion on a gel-like film of another one has been studied. The structural characteristics of the multilayer composites and their components have been analyzed by X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray microanalysis. A technique is proposed for studying the structure of surface layers of thin polymer films (15–20 μm) using a portable DIFREI-401 diffractometer. It is shown that the sequence of layer deposition during the formation of membrane films does not affect their structural characteristics. The interaction between positively charged chitosan groups (-NH3+) and negatively charged sulfoethyl cellulose groups (-SO3−) during the growth of polyelectrolyte complexes results in a packing of chitosan chains in the multilayer film.

Preparation and analysis of multilayer composites based on polyelectrolyte complexes

A method for preparing multilayer film composites based on chitosan has been developed by the example of polymer pairs: chitosan–hyaluronic acid, chitosan–alginic acid, and chitosan–carrageenan. The structure of the composite films is characterized by X-ray diffractometry and scanning electron microscopy. It is shown that the deposition of a solution of hyaluronic acid, alginic acid, or carrageenan on a chitosan gel film leads to the formation of a polyelectrolyte complex layer at the interface, which is accompanied by the ordering of chitosan chains in the surface region; the microstructure of this layer depends on the nature of contacting polymer pairs.

Peculiarities of the microstructure of a nanoscale modification of η-TiO2

Samples with nanoscale η-TiO2 phase have been obtained by sulfate and modified sulfate methods and are characterized by a complex of techniques: X-ray diffraction, electron diffraction, small-angle X-ray scattering (SAXS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy, and X-ray energy-dispersive analysis. The effect of sample formation conditions on the size and shape of crystallites, content of the amorphous component in the samples, and their elemental composition has been established. A significant change (depending on the synthesis conditions) in the parameters of the diffraction reflection with d ∼ 17–21 Å (intensity and interplanar spacing d, Å), pronounced for η-TiO2, is revealed. This change is most likely related to the variation in the content of water molecules in the interlayer space of η-TiO2 structure and/or the change in crystallite shape.

Low-voltage scanning electron microscopy of multilayer polymer systems

The possibilities of low-voltage scanning electron microscopy for visualization of specific features of the microstructure in internal layers of multilayer polymer films are demonstrated by the example of “chitosan–polyelectrolyte complex–alginic acid” composite. The process of electron beam interaction with a sample at low electron energies is considered. The key parameters of low-voltage electron microscopy, which make it possible to increase the resolution of SEM images of polymer systems, are discussed.

Rheological Features of Fiber Spinning from Polyacrylonitrile Solutions in an Electric Field. Structure and Properties

Spatially ordered fibers of diameter 260-990 nm were produced by electrospinning from polyacrylonitrile (PAN) solutions. The influence of the rheological properties of solutions of PAN and its copolymers was investigated over a broad range of molecular weights during fiber spinning in an electric field. The structural and tensile properties of the fibers were studied.

Study of doped higher manganese silicides crystals by transmission electron diffraction and electron backscatter diffraction

The microstructure of Al-, Ge-, and Mo-doped higher manganese silicide crystals (HMS), grown by the Bridgman method have been investigated by transmission electron diffraction, electron backscatter diffraction, scanning electron microscopy, and X-ray energy-dispersive spectrometry. It is shown that the matrix crystal has the Mn4Si7 structure. The introduction of Ge and Mo impurities into an HMS crystal results in the precipitation of Si-Ge solid solution and molybdenum disilicide. The size of precipitates varies in a wide range: from several nanometers to several hundreds of micrometers. The following orientation relationships between Ge-Si precipitates and the Mn4Si7 crystal were determined: (112)

Study of structural order in porphyrin-fullerene dyad ZnDHD6ee monolayers by electron diffraction and atomic force microscopy

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Two-Ply Composite Membranes with Separation Layers from Chitosan and Sulfoethylcellulose on a Microporous Support Based on Poly(diphenylsulfone-N-phenylphthalimide)

Ge-Si ‖ (010)[100] Mn4Si7. Polycrystalline MoSi2 precipitates form a multicomponent texture along the [001] Mn4Si7 direction. Small amounts of cubic MnSi and Al-Mn-Si alloy precipitates were revealed. In addition, Al oxide was observed mainly in crystal pores. It is shown that 0.5–0.8 at % Al, 0.4–0.6 at % Mo, and 1.5–2.0 at % Ge impurities are incorporated into the Mn4Si7 lattice.