Investigation of the thermal behavior of new silica-polymer anion exchangers

The thermal properties of new anion exchangers consisting of silica core and organic layers grafted onto their surface were evaluated by thermogravimetry and differential scanning calorimetry. The anion exchangers were prepared by chemical modification of bare silica gel. The support was coated with polymeric layers formed by condensation polymerization of primary amines with diepoxides. Synthesized copolymers of methylamine and 1,4-butanedioldiglycidyl ether have a dendrimer structure. By TG/FTIR/MS, it was observed that silica-layered materials exhibited two stages of mass loss: first with T _max1 160 °C, connected with desorption of water molecules from the adsorbents surface, and then with T _max2 390 °C, connected with degradation of organic layers.     

Thermal characterization of polymeric anion exchangers with a dendrimeric structure

The thermal properties of new anion exchangers prepared via the grafting process to polymeric particles having hydroxyl groups on their surface were evaluated by thermogravimetry and differential scanning calorimetry. The support microspheres were copolymers of 1,4-di(2-hydroxy-3-methacryloyloxypropoxy)benzene (1,4 DMH) and trimethylolpropane trimethacrylate (TRIM). They were coated with polymeric layers formed by condensation polymerization of primary amines with diepoxides. Synthesized copolymers of methylamine and 1,4-butanedioldiglycidyl ether have a dendrimer structure. By TG/FTIR/MS, it was observed that new dendrimeric materials exhibited one stage of mass loss with T _max1 400 °C, connected with degradation of organic layers. DSC and TG experiments showed that water molecules are absorbed on the materials surface. The synthesized anion exchangers exhibited good thermal stability, suitable for their use in chromatographic experiments carried out with higher temperatures.     

Reactions of group 13 metal trialkyls with oxamides

Alkyl aluminum-, gallium-, and indium oxamidates Me₄Al₂(dpoa) (1), Me₄Al₂(dboa) (2), Me₄Ga₂(dpoa) (3), Me₄Ga₂(dboa) (4), ^tBu₄Ga₂(dpoa) (5) and Me₄In₂(dboa) (6) (dpoa-H₂ = N,N′-diphenyloxamide, dboa-H₂ = N,N′-di-tert-butyloxamide) have been prepared and characterized. Compounds 1-3, 5 and 6 exist in the form of isomers a only, with a skeleton framework of the molecules consisting of two almost flat, coplanar and fused MNOC₂ (M = Al, Ga, In) heterocyclic rings. Depending on the reaction conditions, the compound 4 was obtained as the isomer 4a or as the mixture of two isomers 4a and 4b. Molecular structures of the compounds 1a-6a have been determined by X-ray crystallography. A structure of the isomer 4b was proposed on the basis of NMR spectroscopy. A skeleton framework of the 4b molecule consists of two fused different cycles, GaO₂C₂ and GaN₂C₂.     

Growth of sapphire crystals for optoelectronics from alumina in a protective medium

This paper reports on the results obtained during the development of the technological process of growth of sapphire crystals for optoelectronics through horizontal directional crystallization in a gaseous argon medium at a pressure of 800 mmHg. The sapphire crystals intended for the use in optoelectronics have been grown from purified molten alumina according to the authors’ technology. It has been demonstrated that, under conditions of a high temperature gradient across the crystallization front and at a low content of reducing components (H₂, CO) in the growth medium, it is possible to grow sapphire crystals satisfying the requirements of optoelectronics.     

Encapsulation of Bovine Serum Albumin in Temperature‐Programmed “Shell‐in‐Shell” Structures

A novel approach to load a hydrophilic bovine serum albumin into drug carriers was proposed in terms of temperature‐programmed “shell‐in‐shell” structures, which were fabricated with poly(N‐isopropylacrylamide), poly(lactide), poly(ethylene glycol), and Au nanoparticles. Spherically well‐defined “shell‐in‐shell” structures were constructed by a modified‐double‐emulsion method (MDEM). The lower critical solubility temperature of the structures was manipulated to 36.4 °C which was confirmed by UV/Vis spectroscopy and DSC (Differential Scanning Calorimetry).

TEM image of the Au@PLLA‐PEG@PNIPAAm‐PDLA structure.     

Chain Architecture Dependent 3‐Dimensional Supramolecular Assembly of Rod‐Coil Molecules with a Conjugated Hexa‐p‐phenylene Rod

Summary: We have prepared hexa‐p‐phenylene based rod‐coil molecules with identical coil volume fractions, but different poly(propylene oxide) (PPO) coil architectures (linear versus dibranched), and investigated their self‐assembling behavior in the solid state by small angle X‐ray scattering (SAXS) and transmission electron microscopy (TEM) techniques. Rod‐coil molecules with a linear PPO coil showed a honeycomb‐like lamellar assembly of rod segments with hexagonally arrayed PPO coil perforations. In contrast, the rod‐coil molecules with dibranched PPO coils self‐organized into rod bundles with a body centered tetragonal symmetry surrounded by a PPO coil matrix. These results demonstrate that the steric hindrance at the rod/coil interface arising from coil architectural variation is a dominant parameter governing supramolecular rod assembly in the rod‐coil system.

TEM images and schematic illustrations of the self‐assembled structures of rod‐coil molecules with linear (left) and dibranched (right) PPO coils, respectively.     

The defects in Se-doped InSb single crystals

Using optical microscopy and TEM methods as well as X-ray topography method structural perfection of Czochralski grown Se-doped InSb single crystals has been investigated. Se concentration was determined by mass-spectrometry method and was in the range of 1.10¹⁷ to 9.10¹⁹ cm⁻³. – It has been shown that Se presence up to the highest concentration does not influence crystal dislocation structure, but gives rise to the large number of precipitates showing moiré contrast. The size of the precipitates is in the range of 0.5 μm to 3.8 μm. From the calculation of the contrast it has been grown that lattice parameter of the precipitates differs from that of matrix by 0.02 ÷ 0.05 Å. – Besides, in crystals with high Se concentration (9.10¹⁹ cm⁻³) small particles with symmetrical field of deformation appear.