Preparation of surfactant-free nanoparticles of methoxy poly(ethylene glycol)-<Emphasis Type="Italic">b</Emphasis>-poly(D,L-lactide-<Emphasis Type="Italic">co</Emphasis>-glycolide-<Emphasis Type="Italic">co</Emphasis>-ɛ-caprolactone)

Surfactant-free nanoparticles of methoxy poly(ethylene glycol)-b-poly(D,L-lactide-co-glycolide-co-ɛ-caprolactone) diblock copolymers (MPEG-b-PDLLGCL) with different DLL:G:CL ratios were prepared by modified-spontaneous emulsification solvent diffusion method. Sizes of resulted colloidal nanoparticles obtained from light-scattering analysis were in the range of 121–132 nm with narrow size distribution. The nanoparticle sizes depended on the composition of the PDLLGCL block. Scanning electron microscopy demonstrated that the nanoparticles were aggregated after drying process, suggested they were soft nanoparticles. However, their initial aggregates can be observed and it was shown that the nanoparticles have spherical shape with smooth surface. The text was submitted by the authors in English.     

Synthesis and thermal properties of parent and modified DMN–<Emphasis Type="Italic">co</Emphasis>-GMA copolymers

The crystal structure, the unit cell parameters and the extent of mullitization were determined, using the Rietveld method, for range of mullite matrix formulations in which kyanite is used as particles reinforcement. The results combined with the mechanical properties and microstructure indicated the effectiveness of the kyanite particles to enhance the strength (>200 MPa), the Vickers hardness (>11 GPa) and the elastic modulus (150 GPa). The strengthening mechanism was particularly linked action of particles reinforcement. At low temperature, kyanite acts as fillers reducing the porosity and playing the role of nucleation sites for the crystallization of metakaolin to mullite. At high temperature (>1350 °C), kyanite decomposes to mullite avoiding the grain growth of the existing crystals and delaying the densification. The extent of the reduction in porosity and the extreme limitation of the liquid phase ensure the homogeneity and the refractoriness that justify the strength enhancement. The unit cell parameters and the crystal structure confirmed predominance of the mullite 3:2 with their small grain size being one of the most stable mullite phases. The small size of their particles and the continuity into the mullite matrix composites allow good packing process for the optimum characteristics achieved: strength, microstructure and thermal expansion coefficient.     

Synthesis of imidazo[4,5-<Emphasis Type="Italic">e</Emphasis>]benzo[1,2-<Emphasis Type="Italic">c</Emphasis>;3,4-<Emphasis Type="Italic">c</Emphasis>´]difuroxanes

A method for the synthesis of imidazo[4,5-e]benzo[1,2-c;3,4-c´]difuroxanes, potential nitric oxide donors, has been developed. The synthesized compounds were characterized by IR and NMR spectroscopy, high resolution mass spectrometry, and elemental analysis.     

<Emphasis Type="Italic">N</Emphasis>-arylsulfanyl-<Emphasis Type="Italic">N</Emphasis>-arylsulfonyl(acyl)-<Emphasis Type="Italic">N</Emphasis>′-phenylthiourea sodium salts

Reactions of N-arylsulfonyl(acyl)arenesulfenamide sodium salts with phenyl isothiocyanate afforded N-arylsulfanyl-N-arylsulfonyl(acyl)-N-phenylthioura sodium salts which were found to increase thermal stability of finely dispersed poly(vinyl chloride).Translated from Zhurnal Organicheskoi Khimii, Vol. 40, No. 10, 2004, pp. 1532–1535.Original Russian Text Copyright © 2004 by Koval, Oleinik.     

Properties of a poly(ethylene glycol)-<Emphasis Type="Italic">block</Emphasis>-poly(<Emphasis Type="Italic">γ</Emphasis>-benzyl <Emphasis Type="SmallCaps">l</Emphasis>-glutamate)-<Emphasis Type="Italic">graft</Emphasis>-poly(ethylene glycol) copolymer membrane

Poly(ethylene glycol)-block-poly(γ-benzyl l-glutamate)-graft-poly(ethylene glycol) (PEG-block-PBLG-graft-PEG) copolymer was synthesized by the ester exchange reaction of PBLG-block-PEG copolymer with a PEG chain. Surface morphology of the PEG-block-PBLG-graft-PEG copolymer membrane was characterized by atomic force microscopy (AFM). Mechanical and chemical properties of the PEG-block-PBLG-graft-PEG copolymer membrane were investigated by tensile testing and contact angle testing. The effects of grafting ratio on the properties of PEG-block-PBLG-graft-PEG copolymer membrane were primarilly studied.     

Synthesis and reactivity of 2-(2-furyl)-1,7-dimethyl-1<Emphasis Type="Italic">H</Emphasis>,7<Emphasis Type="Italic">H</Emphasis>-benzo[1,2-<Emphasis Type="Italic">d</Emphasis>: 3,4-<Emphasis Type="Italic">d</Emphasis>′]diimidazole

2-(2-Furyl)-1,7-dimethyl-1H,7H-benzo[1,2-d: 3,4-d′]diimidazole was synthesized by the Weidenhagen reaction followed by N-methylation. Electrophilic substitution reactions of the title compound (nitration, bromination, sulfonation, formylation, and acylation) involved both the furan ring and central benzene fragment.     

Synthesis of New Thieno[2,3-<Emphasis Type="Italic">b</Emphasis>:5,4-<Emphasis Type="Italic">c</Emphasis>′]dipyridines

Summary. We describe the formation of thieno[2,3-b:5,4-c]dipyridines from 5,6-dihydropyridine-2(1H)-thiones. The two-step reaction mechanism was revealed by isolation of an intermediate. The oxo and thioxo groups of the obtained tricyclic compounds were hydrogenated selectively. The structures of all new compounds were elucidated by NMR experiments.Received December 17, 2002; accepted December 20, 2002 Published online June 2, 2003     

Crystallization of novel poly(ε-caprolactone)-<Emphasis Type="Italic">block</Emphasis>-poly(propylene adipate) copolymers

Poly(ε-caprolactone)-block-poly(propylene adipate) (PCL-block-PPAd) copolymers were prepared using a combination of polycondensation and ring opening polymerization of ε-CL. ¹H-NMR and ¹³C-NMR spectroscopy showed that the prepared copolymers were block. Also, the copolymer composition was calculated from NMR spectra and was found similar to the feeding ratio. The copolymers formed PCL crystals as was proved by WAXD. The crystallization rates and degree of crystallinity, measured from DSC crystallization experiments, decreased with PPAd content. The equilibrium melting points of PCL were estimated applying the Hoffmann–Weeks method and the observed melting point depression was analyzed using the Nishi–Wang equation which showed that there is some miscibility of the copolymer segments. Isothermal crystallization experiments after self-nucleation were performed to distinguish the nucleation and crystal growth stages during isothermal crystallization. The secondary nucleation theory was then used and the obtained data for crystallization rates, estimated from the inverse of the crystallization half-times, were analyzed. The resulting values for nucleation constant K _g, and also for the surface free energies and work of chain folding, increased with PPAd content due to topological restrictions.     

Physicochemical properties and complexing ability of <Emphasis Type="Italic">N</Emphasis>-(2-ethylhexanoyl)-<Emphasis Type="Italic">N</Emphasis>′-sulfonylhydrazines

The effect of substituent at the sulfonyl group on the physicochemical properties and complexing ability of the sulfonyl derivatives of 2-ethylhexanoic acid hydrazide of the general formula C₄H₉CH(C₂H₅)C(O)·NHNHSO₂C₆H₅R [R = H, CH₃, NO₂, NHC(O)CH₃, Cl] with respect to Cu(II), Co(II), and Ni(II) ions was studied.     

Modification of poly(vinyl alcohol) membrane via blending with poly(<Emphasis Type="Italic">γ</Emphasis>-benzyl <Emphasis Type="SmallCaps">l</Emphasis>-glutamate)-<Emphasis Type="Italic">block</Emphasis>-poly(ethylene glycol) copolymer

A series of poly(vinyl alcohol) (PVA)/poly(γ-benzyl l-glutamate)-block-poly(ethylene glycol) (PBLG-b-PEG) blend membranes with different PVA/PBLG-b-PEG mole ratios were prepared by pervaporation. Structure and morphologies of PVA/PBLG-b-PEG blend membranes were investigated using Fourier transformation infrared spectroscopy (FTIR), and atomic force microscopy (AFM). Mechanical and chemical properties of PVA/PBLG-b-PEG blend membrane were studied by tensile testing and other physical methods. It was revealed that the introduction of PBLG-b-PEG copolymer has significant effect on the properties of a PVA membrane.     

Tri-<Emphasis Type="Italic">p</Emphasis>-Tolylbismuth Diperchlorate and μ-Oxo-bis[(perchlorato)tri-<Emphasis Type="Italic">p</Emphasis>-tolylbismuth]: Synthesis and Structure

Tri-p-tolylbismuth perchlorate (1) and μ-oxo-bis[(perchlorato)tri-p-tolylbismuth] (2) have been synthesized by the reaction between tri-p-tolylbismuth dibromide and silver perchlorate and its hydrate. The complexes have been studied by chemical analysis, IR spectroscopy, and X-ray diffraction. Complex 1 is triclinic, space group Pī, Z = 4, a =10.7271(9) Å, b = 13.5585(11) Å, c = 18.1592(13) Å, α = 110.867(3)°, β = 94.944(3)°, γ = 96.888(3)°, V = 2426.3(3) Å3, ρ_calcd = 1.865 g/cm3; complex 2 crystallizes in trigonal symmetry, space group R\(\bar 3\), a = 13.1157(2) Å, c = 22.1959(2) Å, γ = 120°, V = 3306.64(8) ų, ρ_calcd = 1.777 g/cm³. The bismuth atoms in the molecular structure of complex 1 have a distorted trigonal bipyramidal coordination to the apically arranged oxygen atoms of perchlorate ions (Bi–C, 2.180(5)–2.201(5) Å; Bi–O, 2.324(4)–2.355(4) Å; OBiO axial angles, 170.1(1)°, 174.5(1)°). The structure of complex 2 contains binuclear [p-Tol₃Bi(ClO₄)]₂O molecules (Bi–O, 2.371(15), 1.9107(7) Å; OBiO axial angle, 180.0°).     

Photoinduced electron transfer reaction of mono-(6-deoxy-<Emphasis Type="Italic">p</Emphasis>-nitrobenzylamino)-<Emphasis Type="Italic">β</Emphasis>-cyclodextrin with naphthalene derivatives

The fluorescence of a number of naphthalene derivatives was quenched by 6-deoxy-p-nitrobenzylamino--cyclodextrin (NACD) in aqueous solution. The origin of the quenching was attributed to the electron transfer from the excited naphthalene groups to the ground state p-nitrobenzyl group of NACD. Both steady-state and time-resolved fluorescence measurements revealed that there were two routes of electron transfer, i.e. (1) electron transfer between the free donor and free acceptor in solution and (2) electron transfer between the donor and acceptor bound in a supramolcular assemble. The evidence collected demonstrates that the latter route was very efficient. As a result, the electron transfer rate and quantum yield of the fluorescence quenching in the present host-guest system were appreciably large.     

Factors influencing aggregation behavior of poly(<Emphasis Type="Italic">γ</Emphasis>-benzyl <Emphasis Type="SmallCaps">l</Emphasis>-glutamate)-<Emphasis Type="Italic">graft</Emphasis>-poly(ethylene glycol) copolymer in mixed solvents

Poly(γ-benzyl l-glutamate)-graft-poly(ethylene glycol) (PBLG-graft-PEG) copolymer was synthesized by the ester exchange reaction of PBLG homopolymer with mPEG. Aggregation behavior of the PBLG-graft-PEG copolymer in mixtures of ethanol and chloroform was investigated by transmission electron microscopy (TEM), dynamic light scattering (DLS), and viscometry. Effects of the polymer solution concentration, grafting degree, test temperature, and chloroform content on the morphology, average particle diameter, and critical micelle concentration (CMC) of the micelles formed by the PBLG-graft-PEG copolymer in the mixed solvents were mainly studied. It was revealed that the PBLG-graft-PEG copolymer can self-assemble into polymeric micelles with a core-shell structure in various shapes depending on the preparation conditions.     

Synthesis of <Emphasis Type="Italic">N</Emphasis>-nitro-<Emphasis Type="Italic">N</Emphasis>′-(trimethylsilyl)carbodiimide

Nitration of N,N′-bis(trimethylsilyl)carbodiimide with N₂O₅ or (NO₂)₂SiF₆ afforded N-nitro-N´-(trimethylsilyl)carbodiimide, the first representative of N-nitro carbodiimides. Its further nitration led to the release of CO₂, which is presumably formed in the course of N,N´-dinitrocarbodiimide decomposition. The reactions of N-nitro-N´-(trimethylsilyl)carbodiimide with nucleophiles take place both at the tri methylsilyl group (for example, with NH₃) to give nitrocyanamide salts and at the carbodiimide C atom (for example, with Et₂NH) to give the corresponding nitroguan idines.     

Ringed spherulites in ternary polymer blends of poly(<Emphasis Type="Italic">ε</Emphasis>-caprolactone), poly(styrene-<Emphasis Type="Italic">co</Emphasis>-acrylonitrile), and polymethacrylate

The relationship between ringed spherulite morphology, crystallization regimes/kinetics, and molecular interactions in miscible ternary blends of poly(-caprolactone) (PCL), poly(benzyl methacrylate) (PBzMA), and poly(styrene-co-acrylonitrile) (SAN) was investigated by using differential scanning calorimetry (DSC), polarized optical microscopy (POM), and wide-angle X-ray diffraction (WAXD). The interactions resulted in the deviation of both experimental and calculated T_gs and formation of the specific morphology of the spherulitic structure. Ring-banded spherulites were observed in the PCL/PBzMA/SAN ternary blends. The width of ring bands changed with the blend ratio and the crystallization temperature. Additionally, both composition and wt% of AN in the SAN copolymer had an apparent effect on the morphology of PCL spherulites. Both the crystallization structure of lamellae and molecular interactions greatly influenced the ring bands of PCL spherulites. Furthermore, by using the Flory–Huggins approximation, the depression of the melting point showed that interactions in the PCL/PBzMA/SAN-17 blend were greater than in the PCL/PBzMA/SAN-25 blend. In the ternary blends, the great molecular interactions between amorphous and crystalline polymer resulted in better homogeneity and a larger band period of the extinction rings in the PCL spherulites.     

Rhodium(I) pentasubstituted cationic complexes on the basis of 1,2-<Emphasis Type="Italic">O</Emphasis>-Alkylidene-3,5,6-<Emphasis Type="Italic">O</Emphasis>-phosphinetriyl-α-<Emphasis Type="SmallCaps">D</Emphasis>-glucofuranose

Reaction of 1,2-O-alkylidene--D-glucofuranose 3,5,6-phosphites with dicarbonylrhodium(I) acetylacetonate was studied. The structure of the reaction products is determined by the reagent ratio. At a 5:1 molar ratio, the step ligand-exchange process yields chiral complexes of the [RhL₅]⁺acac^– type. Dynamics of and anion exchange in these complexes are considered.Translated from Zhurnal Obshchei Khimii, Vol. 74, No. 9, 2004, pp. 1418–1421.Original Russian Text Copyright © 2004 by A. Koroteev, Teleshov, M. Koroteev, and Nifantev.This revised version was published online in April 2005 with a corrected cover date.     

Synthesis and investigation of poly(p-phenylenediamine)–poly(1,4-benzoquinonediimine-<Emphasis Type="Italic">N,N</Emphasis>-diyl-1,4-phenylene)

Poly(1,4-benzoquinonediimine-N,N-diyl-1,4-phenylene) having similar structure to pernigraniline was synthesized by chemical oxidative polymerization of p-phenylenediamine and its salt using potassium peroxydisulfate as an oxidant in molar ratio 1:0.8, in acetic acid, at 278 K. Acetylation of amino end groups of polymers were carried out aiming to prevent self-condensation of amino groups with 1,4-benzoquinone diimine groups by 1,4-addition. Attempting to carry out the reduction of obtained polymer with hydrazine hydrate, it was shown that 1,4-addition of hydrazine to quinonediimine groups occurs instead of expected reduction reaction. When doping obtained polymers with iodine, the electrical conductivity increases up to 10^?4 S/cm.     

Highly Efficient Regioselective Synthesis of 5′-<Emphasis Type="Italic">O</Emphasis>-lauroyl-5-azacytidine Catalyzed by <Emphasis Type="Italic">Candida antarctica</Emphasis> Lipase B

Enzymatic regioselective acylation of 5-azacytidine with vinyl laurate was successfully conducted with an immobilized lipase from Candida antarctica type B (i.e., Novozym 435) for the first time. The acylation of 5-azacytidine took place at its primary hydroxyl group and the desired product 5′-O -lauroyl-5-azacytidine could be prepared with high reaction rate, high conversion, and excellent regioselectivity. The influences of several key variables on the enzymatic acylation were also systematically examined. Pyridine was found to be the best reaction medium. The optimum initial water activity, the molar ratio of vinyl laurate to 5-azacytidine and reaction temperature were 0.07, 30:1, and 50 °C, respectively. Under the optimized conditions described above, the initial reaction rate, the substrate conversion, and the regioselectivity were as high as 0.58 mM/min, 95.5%, and >99%, respectively, after a reaction time of around 5 h.     

1,3-Diamino-2-Hydroxypropane-<Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>′,<Emphasis Type="Italic">N</Emphasis>′-Tetraacetic Acid: Crystal and Molecular Structures

The synthesis, IR spectroscopic study, and X-ray diffraction analysis (CIF file CCDC no. 1574078) are carried out for 1,3-diamino-2-hydroxypropane-N,N,N′,N′-tetraacetic acid (I). The structural units of a crystal of compound I are (H_4.5HPdta)^0.5– anions, (H_5.5HPdta)^0.5+ cations, and molecules of water of crystallization joined by a branched network of hydrogen bonds: strong intermolecular O–H…O and intramolecular N–H…O bonds.     

Characteristics of the hydrogen bond and the structure of Н-complexes of <Emphasis Type="Italic">p</Emphasis>-n-propyloxybenzoic acid and <Emphasis Type="Italic">p</Emphasis>-n-propyloxy-<Emphasis Type="Italic">p</Emphasis>′-cyanobiphenyl

The conformational properties of p-n-propyloxybenzoic acid and p-n-propyloxy-p′-cyanobiphenyl molecules, which can exhibit liquid crystalline properties in the formation of Н-complexes, are studied (DFT/B3LYP)/cc-pVTZ method). It is found that a molecule of p-n-propyloxybenzoic acid has 16 conformers that can be divided into four groups with respect to relative energies (0 kcal/mol, 1.6 kcal/mol, 6.5 kcal/mol, and 8.1 kcal/mol), and a molecule of p-n-propyloxy-p′-cyanobiphenyl has six conformers with relative energies of 0 kcal/mol (two conformers, φ(С_Ph–O–C–C)=180°) and 1.6 kcal/mol (four conformers, φ(С_Ph–O–C–C)=64.4°). In all conformers of the 3-AOCB molecule, phenyl rings are turned at 35° relative to each other. A conformation with the planar arrangement of two rings has a higher energy by 1.5 kcal/mol. Barriers to the internal rotation of different groups are determined and it is established that the structural nonrigidity of the molecules is mainly due to the possible rotation of the–C₂Н₅ moiety about the C–C bond. It is shown that with increasing temperature the vibrational amplitudes of the OC₃H₇ substituent, which enhance the probabilities of transitions between the conformers, become appreciably larger. It is found that p-n-propyloxybenzoic acid and p-n-propyloxy-p′-cyanobiphenyl can form Н-complexes with the medium hydrogen bond. Two types of the structural organization of Н-complexes are considered: linear and angular. The similarity of energies of Н-complexes with different structures (NBO analysis) can be the reason for the occurrence of two liquid crystalline subphases of p-n-propyloxybenzoic acid and p-n-propyloxy-p′-cyanobiphenyl system.