Specific structural features of crystalline regions in biodegradable composites of poly-3-hydroxybutyrate with chitosan

Differential scanning calorimetry and X-ray diffraction at wide and small angles were used to examine the biodegradable composites of poly-3-hydroxybutyrate with chitosan, produced by mixing of these polymers in a rotor disperser at 150°C. Samples of individual polymers and composites with 80, 40, and 20 wt % poly- 3-hydroxybutyrate were studied. It was found that the presence of chitosan in the composites leads to a change in the crystallite size of poly-3-hydroxybutyrate and to an increase in the large period in this polymer. Mixing of poly-3-hydroxybutyrate with chitosan affects the structural rearrangement in crystalline regions of poly-3-hydroxybutyrate under a high-temperature treatment. The effect of a high-temperature treatment of the composites via alternation of melting–crystallization cycles in the nonisothermal mode, when a sample is heated and cooled at the same constant rate of 8 deg min–1 in the range from 20 to 200°C and is annealed at a temperature of 150°C, was analyzed. This analysis suggests that, in composites of this kind, the intermolecular interaction between the components is a factor strongly affecting the structure of the crystalline regions and the mechanism of their rearrangement in the course of annealing. The mechanism of this interaction is discussed.     

Kinetic Aspects of the Adsorption on Aluminum Oxide Drying Agents Doped with Alkali Metal Ions

Fundamental dynamic (kinetic) aspects of the process in which water vapor interacts with the surface of drying agents that are synthesized on the basis of low-temperature modification of aluminum oxide produced from a pseudoboehmite-containing hydroxide and are modified (doped) with alkali atoms (K, Na). It is shown that the kinetics of adsorption on the samples under study, formed from the fine fraction (0.5–1.0 mm) of aluminum oxide adsorbents, can be described with the Glueckauf equation, which rather well describes the dynamics of water vapor absorption in the course of time. The equation parameters were determined: adsorption rate constants and the equilibrium adsorption capacities (a*). It was found that the alkaline modification of the surface of aluminum oxide adsorbents results in that a* increases (by ~40%) as compared with the unmodified drying agent. A correlation is observed between the equilibrium adsorption capacity of the samples under study and the acid-base properties of the surface.     

Variation of the capacity characteristics of a composite material consisting of acetylene black and polytetrafluoroethylene and of its wettability with an aqueous solution under the action of anodic current

The effect exerted by treatment with cyclic anodic current in 1 M H₂SO₄ in the interval 0.0–2.0 V on electrodes made of a porous (55 vol %) composite material consisting of A-437E acetylene black and polytetrafluoroethylene (60 wt %) was studied. The cyclic volt–ampere curves were recorded in 3 M KOH and 1 M H₂SO₄ to determine the double layer capacity. The anodic treatment leads to an increase in the volume of pores filled with the electrolyte and in the electrical capacity of the electrode due both to an increase in the area of the surface wetted with the electrolyte and to the pseudocapacity caused by oxidation of the carbon black surface.     

Distribution of Zinc Oxide Nanocrystals in a Polymer Film

The structure of polymer films modified with zinc oxide nanocrystals was studied by the optical absorption and small-angle X-ray scattering methods. Small-angle X-ray scattering allows determination of the nanoparticle size distribution function, which is the decisive factor in predicting the optical properties of heterophase materials, including filled polymer films. The optical absorption spectrum of an acrylate polymer film doped with 1.6 wt % zinc oxide nanocrystals approaches the ideal absorber spectrum, which allows this material to be recommended for use as a protective color filter.     

Effect of gas environment parameters on operation efficiency of chemical absorbents of carbon dioxide

Effect of main characteristics of the gas medium on the absorbing properties of alkaline chemical absorbents is demonstrated. The following gas flow parameters were examined as variables: carbon dioxide content of the gas flow within the range 0.2–5.0 vol %, gas humidity of 25–90 rel %, and pressure in the zone of the chemisorption process in the range from 2 to 6 MPa. As objects of study served mixed chemical absorbents based on calcium, sodium, and lithium hydroxides.     

Synthesis of basic bismuth(III) oxalate by precipitation from nitrate solutions

Conditions were determined in which basic bismuth oxalate of composition BiC₂O₄(OH) can be obtained by direct precipitation upon addition of oxalic acid from nitrate solutions used in production of bismuth compounds. The composition of the compound was confirmed by X-ray phase and chemical analyses, IR and Raman spectroscopy, and thermogravimetry. Electron microscopy was used to examine the effect of the composition of the reaction medium and temperature on the morphology of the product being obtained. It was shown that β-Bi₂O₃ can be obtained in oxidative thermolysis of basic bismuth oxalate, depending on its morphology.     

Preparation and hydrophobizing properties of carboxylic acid <Emphasis Type="Italic">N</Emphasis>-[3-(dimethylamino)propyl]amide hydrochlorides

Carboxylic acid N-[3-(dimethylamino)propyl]amides were prepared in 90–95% yield by the reaction of carboxylic acid esters with N,N-dimethyl-1,3-diaminopropane in the presence of zeolites as catalysts. Hydrochlorides of these amides show promise as cationic surfactants for hydrophobization of the bottomhole formation zone of oil fields.     

Сyclization of 1-amino-2-hydrazinobenzimidazole treated with carbon disulfide. Synthesis of 9-amino-2,9-dihydro-3<Emphasis Type="Italic">Н</Emphasis>-[1,2,4]triazolo[4,3-<Emphasis Type="Italic">а</Emphasis>]benzimidazole-3-thione and its derivatives

1-Amino-2-hydrazinobenzimidazole when treated with carbon disulfide underwent a regioselective cyclization involving the hydrazino group to form 9-amino-2,9-dihydro-3Н-[1,2,4]triazolo[4,3-а]benzimidazole-3-thione. Being an N-amine this compound gives Schiff bases with aromatic aldehydes, and as thione in DMF at a temperature not exceeding 60°С it is successfully alkylated, particularly by functionalized alkylating agents, affording the corresponding sulfanylmethyl derivatives. In boiling DMF, as it is demonstrated by an example of benzyl chlorides, NNH₂ group also undergoes alkylation that unexpectedly results in 4-benzylidenamino-3-benzylsulfanyltriazolobenzimidazoles.     

Stereoselective synthesis of tri- and tetrasubstituted tetrahydropyrans from <Emphasis Type="Italic">syn</Emphasis>- and <Emphasis Type="Italic">anti</Emphasis>-1-R-2-(4-bromophenyl)-5-methylhex-4-en-1-ols and some chemical transformations of the products

Tri- and tetrasubstituted tetrahydropyranes fused to one and two heterocycles with various functional groups (COOEt, Br, MeC=CH₂) were synthesized in stereoselective fashion by reactions of syn- and anti-1-R-2-(4-bromophenyl)-5-methylhex-4-en-1-ols (R = Bu, PhCH₂) with trifluoromethanesulfonic acid, aldehydes in the presence of boron trifluoride–diethyl ether complex (Prins reaction), and salicylaldehydes in the presence of trimethyl orthoformate and p-toluenesulfonic acid. The obtained compounds were brought into Suzuki coupling with thiofen-2-ylboronic acid, hydrolysis, and reduction of the ester group with lithium tetrahydridoaluminate. The resulting carboxylic acid was converted to carboxamide, and the alcohol was oxidized to aldehyde which was converted to oxime. The steric configuration of substituents remained unchanged in all chemical transformations.     

Synthesis of fused derivatives of 1,8-naphthyridine

Reactions of aromatic aldehyde, 2-aminoprop-1-ene-1,1,3-tricarbonitrile and cyclic enhydrazinoketones led to the formation of N-substituted 5-aryl-2,4-diamino-6-oxo-5,6,7,8,9,10-hexahydrobenzo[b][1,8]- naphthyridine-3-carbonitriles