Poly[3,3-bis(azidomethyl)oxetane]–2,4-dinitro-2,4-diazapentane

Constructing phase diagrams for the mixtures of semicrystalline polymers and low molecular mass substances by DSC can meet with difficulties in the case of slow polymer crystallization. A problem of this kind is encountered for high-energy compositions poly[3,3-bis(azidomethyl)oxetane] (PBAMO)–2,4-dinitro-2,4-diazapentane (DNAP). In this study, the experimental phase diagram PBAMO–DNAP is constructed by an optical method, which makes it possible to visualize structural transformations. The kinetic studies by DSC and XRD reveal that 30–50 days of storing a homogenized PBAMO–DNAP mixture at room temperature are needed to attain stationary values of the crystallinity degree and heat of fusion. Even after that, the DSC method cannot deliver a solubility curve of DNAP in PBAMO, which is naturally generated by the optical method. This curve separates a domain of physical gels, effectively crosslinked by polymer crystallites and swollen with the plasticizer molecules, from a two-phase domain, in which the above gel reaches osmotic equilibrium with the pure plasticizer. It is also shown that the melting temperature of DNAP drops with growing the PBAMO content in the mixture, which is consistent with a decrease in the mean size of plasticizer crystals formed in polymer pores during the previous cooling.     

The Crystallinity of γ-Irradiated Poly(tetrafluoroethylene)

The influence of absorbed -radiation dose over the range 0–220 kGy on the heat of fusion and the crystallinity of industrial specimens of bulk PTFE and PTFE films were studied using the techniques of adiabatic and differential scanning calorimetry. The thermodynamic characteristics of transitions in the interval 287–310 K in the original and the irradiated polymer were determined. Based on the results obtained, a new crystal modification other than the one present in the unirradiated material was assumed to be formed during -irradiation.     

On the lineshape of νas(NO2) in nitrate esters: 3,3-bis(nitratomethyl)oxetane

The anomalously large splitting and low intensity of ν_as(NO₂) in solid 3,3-bis(nitratomethyl)oxetane, O(CH₂)₂C(CH₂ONO₂)₂, is attributed to the effects of vibrational coupling based on a variable temperature study of the internal modes. In acetone-d₆ solution conformational isomer equilibria involving the ONO₂ groups appear to exist that are manifested in ν_as(NO₂). This compound indicates that both isomerization and vibrational coupling should be kept in mind when using ν_as(NO₂) to obtain structural information on nitrate esters.     

Cationic ring-opening polymerization of 3,3-bis（chloromethyl）oxacyclobutane in ionic liquids

Cationic ring-opening polymerization of 3,3-bis(chloromethyl)oxacyclobutane catalyzed by BF_3·OEt_2 was carried out in ionic liquids [bmim]BF_4 and [bmim]PF_6.The influences of BCMO concentration and molar ratio of BCMO/BF_3·OEt_2 on the molecular weights and yield of PBCMO were investigated.The polymerization in ionic liquids proceed to high conversions,although molecular weights are limited,similar to polymerization in organic solvent such as CH_2Cl_2.Follow a viewpoint of green chemistry, we feel ionic liquid [bmim]BF_4 is superior to [bmim]PF_6.Extracting [bmim]PF_6 from the product using organic solvent as extractant limits its advantage as a green reaction media.     

Poly [ (chloromethyl) styrene-co-divinylbenzene] Continuous Rod Column of Weak Cation Exchange Chromatography and its Applications in the Separation of Biopolymers

IntroductionFordecades,macroporouspolymericbeadshavebeenwidelyemployedasakindofchromatographicmatrixfortheanalysisandseparationofproteins.However,someinherentdrawbacks.suchasthecomplicatedsyntheticprocessortheloweroccupiedspaceinsideachromatographicc...     

Synthesis and spectral properties of 3,3′-bis(dipyrrolylmethene)

Bis(2,4,7,8,9-pentamethyldipyrrolylmethene-3-yl)(4′-methoxyphenyl)methane dihydrobromide was synthesized and its spectral properties were studied. It was found that the basicity of the ligand 3,3′-bis-(dipyrrolylmethene) decreases upon insertion of the methoxyphenyl group in the 3,3′-spacer.     

Synthesis and spectral analysis of alkyl-substituted 3,3′-bis(dipyrrolylmethenes)

Four new alkyl-substituted 3,3′-bis(dipyrrolylmethene) dihydrobromides containing from 4 to 10 alkyl substituents were synthesized. In a highly alkylated ligand of these substances one of the hydrogen atoms of the 3,3′-methylene spacer was substituted with a phenyl group. The compounds obtained were studied by IR, ¹H NMR, electron absorption, and fluorescent spectroscopy. The increased alkylation degree of pyrroles and the introduction of an aryl substituent in the 3,3′-spacer causes a significant high-frequency shift of the N-H stretching vibrations in the IR spectra, an upfield shift of the NH-proton signals in 1H NMR spectra, a decrease in the auxochromic effects of protons on the aromatic system of chromophore in the composition of salts. The red shift of maximum of the strong band in electron absorption spectra and the emission spectra of compounds in DMF, DMSO, C₅H₅N, C₆H₆, and CHCl₃ was established. The salts obtained are stable in benzene and chloroform, while in electron-donor solvents the irreversible processes of solvolytic dissociation of salts to free organic base and HBr take place.     

Complexing properties of N-[1,1-bis(hydroxymethyl)ethyl]-and N-[tris(hydroxymethyl)methyl]-β-alanine

Russian Chemical Bulletin - Protolytic and complexing properties of N-[1,1-bis(hydroxymethyl)ethyl]- and N-[tris-(hydroxymethyl)methyl]-β-alanine were estimated using the potentiometry. Values...     

Spectroscopy of the excited-state complex of zinc(II) with 3,3′-bis(dipyrrolylmethene)

Spectra of nonstationary transient absorption of metal bis(dipyrrolylmethene) complexes in cyclohexane and ethanol, which exhibit different photophysical and photochemical properties in these solvents, have been measured and the yields of excited triplet states have been evaluated. It has been shown that the yield of triplets is determined by the intramolecular structure and the difference in fluorescence and phototransformation yields is due to intermolecular interaction of the excited molecules with the solvation shell.     

Spectrophotometric study of melting of double stranded Poly[A]·Poly[U] in the aqueous solution

Experimentally observed changes in the electronic absorption spectrum of sodium salt of synthetic polyadenyl–polyuridyl acid (Poly[A]·Poly[U]) in the aqueous solution (pH = 7.0, I = 0.15 mol/L) with the change in temperature were explained in terms of co-existence of two different forms of the Poly[A]·Poly[U] strands. Chemometrics analysis of full set of melting curves measured at 120 wavelengths in the UV spectral range has been performed using evolving factor analysis (EFA) and KALS designed for the calculation of equilibrium constants from spectrometry data without a priori set model of the system. Using the Van’t Hoff equation, we have determined thermodynamic constants of the biopolymer transition from the double stranded helix into the random coil conformation (helix–coil transition), they can be further used to quantify the possibility of these structures to be involved in biochemical processes. Molecular model of partially denatured Poly[A]′·Poly[U]′ complex has been biult by means of molecular mechanics.     

π-Stacking interactions at the service of [Cu]-bis(oxazoline) recycling

Anthracene- and pyrene-tagged bis(oxazoline) ligands have been prepared and immobilized on charcoal, fullerene, and single-walled carbon nanotubes through π–π interactions. The corresponding copper complexes have been evaluated for their propensity to promote heterogeneous asymmetric Henry and ene reactions. The best results, in terms of activity, selectivity, and stability toward the recycling procedure have been obtained with the pyrene/SWCNT system, as the first example demonstrating the usefulness of such reversible interactions for the asymmetric formation of new C–C bonds.     

Synthesis and Structure of Bis[2,6-bis(2-pyridylamino)pyridinium] Tetrachlorocadmiumate(II)

1 INTRODUTION The d10 configuration of Cd(II) permits a wide variety of coordination numbers and geometries[1~3]. In recent years, one-, two- and three-dimensional infinite supramolecular coordination assemblies of Cd(II) have been the subject of great interest owing to their potential applications in catalysis, optical properties, clathration, etc[4~8]. In fabricating the coordination assemblies, organic ligands as well as inorganic anions have been observed to control the structural di…     

Studies on the Miscibility of Poly(2‐hydroxyethyl methacrylate) and Poly(ethylene oxide) Blends

Miscibility characteristics of poly[2‐hydroxyethylmethacrylate] (PHEMA) and poly[ethylene oxide] (PEO) have been investigated by solution viscometry, ultrasonic and differential scanning calorimetric (DSC) methods. The interaction parameters were obtained using the viscosity data. Ultrasonic velocity and adiabatic compressibility vs. blend composition have been plotted and are found to be linear. A single glass transition temperature was observed by differential scanning calorimetry. Variation of glass transition temperature (T_g) with composition follows Garden‐Taylor equation. T_g values have also been calculated from the Fox equation. The results obtained reveal that PHEMA forms a miscible blend with PEO in the entire composition range.     

Dehydrochlorination of trichloro(α,β-dichlorophenethyl)-silane and of trichloro[α-chloro-α-(chloromethyl)benzyl]silane

Summary The general character of the rearrangement undergone by ,-dichloroalkyltrichlorosilanes in the course of their dehydrochlorination by means of aluminum chloride was confirmed by reference to a new example of the reaction.     

Polylactones. 13. Transesterification of Poly(L-Lactide) with Poly(Glycoude), Poly(β-Propio-Lactone), and Poly[ε -Caprolactone)

Homogeneous blends of poly(L-lactide) (M _n = 30 000 to 40 000) and poly(β-propiolactone) or poly(ε-caprolactone) were prepared in solution. The solvent-free blends were subjected to transesterification catalyzed by means of methyl triflate, triflic acid, boron trifluoride, or tributyltin methoxide at 100 or 150°C. At 100°C, transesterification was barely detectable even after 96 h. When poly(β-propiolactone) was used as the reactant at 150°C, degradation was faster than transesterification regardless of the catalyst. The same negative result was obtained for heterogeneous blends of poly(L-lactide) and poly(glycolide). In the case of poly(ε-caprolactone), copolyesters with slightly blocky sequences were obtained with tributyltin methoxide as catalyst, whereas the acidic catalysts caused rapid degradation. The copolyesters were characterized by means of ¹H-NMR spectroscopy with regard to their molar composition, by means of ¹³C-NMR spectroscopy with regard to their sequences, and by means of differential scanning calorimetry with regard to crystallinity.     

Photoluminescence and Electroluminescence Properties of 2,5-Bis[2,2′-bis(5-phenyl)-1,3,4-oxadiazole] Thiophene(T-OXD)and T-OXD/Poly(9-vinylcarbazole) Blends

The photoluminescence(PL) and the electroluminescence(EL) properties of a novel organic compound, 2,5-bis(2,2′-bis(5-phenyl)-1,3,4-oxadiazole(T-OXD), were studied in chloroform and in a solid thin film. The PL and the EL properties of T-OXD/poly(9-vinylcarbazole)(PVK) blends were also studied, which contained various contents of T-OXD. The PL maximum emission peaks of T-OXD/PVK blends show gradual bathochromtic-shift with the increase of the T-OXD content. The EL spectra of T-OXD/PVK devices are similar to their PL spectra, and all the EL maximum emission peaks show bathochromtic-shift compared with the corresponding PL spectra, which is ascribed to the formation of electroplex. The turn-on voltages for ITO/T-OXD:PVK/Al devices decreased from 13.5 V of the device cotaining 0.1% T-OXD(mass fraction) to 5 V of the device containing 5% T-OXD, which suggests that T-OXD improves the energy level match between T-OXD and PVK and enhances the emission efficiency. The experimental results indicate that T-OXD can be used as a good electron transporting material.