Studies of aminolysis of acrylonitrile–divinylbenzene–methyl methacrylate copolymers

Aminolysis of nitrilacrylate–divinylbenzene–methyl methacrylate copolymers by diethylenetriamine is studied under various conditions. The effect of temperature and catalyst concentration on the properties of synthesized anion exchangers depending on the duration of aminolysis is investigated. The conditions for synthesizing anion exchangers with high capacity characteristics are proposed according to the study results.     

Excimer fluorescence and structures of the inclusion complexes of β-cyclodextrin with naphthalene and its derivatives

Fluorescence of the inclusion complexes with different compositions formed by naphthalene-h₈, naphthalene-d₈, 2,7-dimethylnaphthalene (DMN), and 2-benzylnaphthalene (BN) with β-cyclodextrin (β-CD) in water was studied. Two types of fluorescence are observed, monomer (MF) and excimer (EF_ fluorescence. The excimer fluorescence of the 2∶2 complex emitted by aggregated light-dispersing crystals forming a precipitate, whereas is the MF is concentrations, EF predominates for the resulting complexes. A proposed structure of the inclusion complexes was derived from MNDO/PM3 semiempirical quantum-chemical calculations. The EF is caused by the structure of the complex, in which both naphthalene molecules are separated by a distance of 4.7 Å: they lie in parallel orientation to each other, whereby one ring is displaced from the other by one-fourth of the length of the naphthalene ring. The complexes of 2,7-DMN and 2-benzylnaphthalene with β-CD do not exhibit EF. For the 2∶2 complex of 2,7-DMN with β-CD, this is due to the fact that the aromatic fragments are removed too far from one another 2-Benzylnaphthalene is unable to form an inclusion complex with β-CD, in whose structure the aromatic fragments inside the cavity could be arranged in parallel planes; instead, it forms a 1∶2 complex with β-CD.     

Chlorosulfonyl styrene–divinylbenzene copolymer characteristics as a function of chlorosulfonation and chlorination reaction parameters

Chlorosulfonyl substituted styrene–divinylbenzene copolymer is a highly reactive intermediate used in organic synthesis. It is obtained in three steps: (1) the polymeric support in the form of spherical beads is prepared by free radical polymerization of styrene; (2) the divinylbenzene mixture and the aromatic styrene groups of the obtained copolymer are sulfonated with chlorosulfonic acid in dichloroethane and (3) this is followed by chlorination of the sulfonyl groups with PCl₅/POCl₃ mixture. Chemical analysis shows that chlorosulfonation leads to both sulfonyl and chlorosulfonyl products in which content and ratio vary as a function of reaction parameters: maximum total group content of 5.1 meq/g is reached after 3 hr reaction, at 40°C with styrene to a chlorosulfonic acid molar ratio of 12.4:1. In the chlorination reaction, sulfonyl to chlorosulfonyl conversion is also observed to vary as a function of time and chlorinating mixture composition: 99.6 mol% conversion degree is attained after 2 hr reaction with styrene/PCl₅/POCl₃ in a molar ratio of 1:4:23. © 1997 John Wiley & Sons, Ltd.     

Reactions of N-(Β-aminoethyl)piperazine and its derivatives

The alkylation, cyanoethylation, and heterocyclization reactoins of N-(-amonoethyl)piperazine and its derivatives, dicarboxylic acid imides, have been investigated. A new method has been proposed for the synthesis of 1,4-diazobicyclo[2.2.2]octane via pyrolytic cleavage of N,N-bis[piperazinoethyl]ethylenediamine.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 381–385, March, 1991.     

Optical properties of polymer blends composed of poly(methyl methacrylate) and ethylene–vinyl acetate copolymer

Optical properties for immiscible polymer blends composed of poly(methyl methacrylate), PMMA, and ethylene–vinyl acetate copolymer (EVA) are studied employing various EVA samples with different vinyl acetate contents. PMMA/EVA shows transparency at room temperature when the difference in refractive index between both phases is small. The light transmittance, however, decreases with increasing the ambient temperature. This phenomenon is attributed to the difference in the volume expansion ratio, leading to the difference in refractive index, between PMMA and EVA. It is found that addition of tricresyl phosphate, TCP, improves the transparency and its temperature dependence. As a result, a ternary PMMA/EVA/TCP blend shows high level of transparency in the wide temperature range, although it has apparent phase separated morphology.     

Mechanochemical and microwave treatment of precipitated zirconium dioxide and study of its physical–chemical,thermal and photocatalytic properties

Journal of Thermal Analysis and Calorimetry - The effects of the microwave treatment (MWT) and mechanochemical treatment (MChT) on the structure and physicochemical properties of precipitated...     

Studies of the chemical properties of tri-n-octylamine–secondary octanol–kerosene–HCl–H2O microemulsions and its extraction characteristics for cadmium(II)

A new microemulsion system is formed by acidification of tri-n-octylamine–secondary octanol–kerosene with HCl. The system is characterized by conductivity measurement, coloring, dilution, infrared spectroscopy and Tyndall effect. The corresponding results show that the microemulsion is oil-continuous (w/o). The phase diagram is also constructed. Conductivities, viscosities, index of refraction, and densities of the microemulsions system are determined. The activation energy (ΔE) is determined at different temperatures, and implies that a bicontinuous structure zone is not found in the investigated system. Additionally, extraction of cadmium(II) ions by this microemulsion system is also investigated. The corresponding optimum extraction conditions are obtained.     

Synthesis and thermal properties of NiSbS–As doped phase

The substitution of Sb with As in the NiSbS intermetallic compound was studied in the framework of evaluating a possible increase of the thermoelectric properties. Different NiSb_1?xAs_xS samples were synthesized with increasing amounts of As (0 < x < 0.66) employing a simple synthetic route using a muffle furnace. Scanning electron microscopy equipped with energy-dispersive X-ray spectroscopy was used to investigate the microstructure. X-ray powder diffraction techniques were employed in order to study the possible existence of a solid solution between NiSbS and NiAsS compounds, as well as to identify the crystal structure and determine the lattice parameters. All compounds were found to crystallise with the NiSbS prototype (cP12-P2₁3), with lattice parameters varying from a = 0.59341(7) nm (x = 0) to a = 0.56849(6) nm (x = 1). Good agreement with Vegard’s law was evidenced. Thermal measurements on NiSb_1?xAs_xS samples were carried out using DTA instruments to evaluate the thermal stability and the melting temperatures.     

Long-lived phosphorescence of aqueous solutions of β-cyclodextrin complexes with naphthalene and its derivatives at room temperature

A long-lived phosphorescence at room temperature (lifetime>1 s) of aqueous solutions of β-cyclodextrin complexes with naphthalene and its derivatives was found. The phosphorescence isobserved for aggregated complexes that form in water a light-scattering suspension, and its low intensity is due to predomination of 2∶2 complexes with efficient excimer fluorescence. Complexes containing isolated aromatic molecules are assumed to be the centers of fluorescence. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2022–2024, October, 1999.     

Preparation and properties of derivatives of dithiolylidene-(4′-phenyldiazonium)acetonitrile

Thefluoroborates of (4,5-dimethyl-1,3-dithiolylidene)-(4-phenyldiazonium)acetonitrile and (4,5-ethylenedithio-1,3-dithiolylidene)-(4-phenyldiazonium)acetonitrile have been prepared; these compounds are photosensitive in the visible region of the spectrum. The quantum yield in the photolysis of the fluoroborates in acetonitrile solution amounts to 0.1 moteleinstein.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, p. 179–181, February, 1994. Original article submitted November 29, 1993.     

Synthesis and properties of functional dyes with squaraine–naphthalene diimide hybrid structure

Naphthalene diimides (NDIs) are promising candidate for electron acceptors due to their low-lying HOMOs and LUMOs. The functinalization of soluble NDIs at the 2,6-position affects the absorption and electrochemical properties. In this study, NDI-based hybrid dyes NDI-SQ-A, B fused with squaraine chromophore were designed and synthesized in order to elucidate the effects of the substitution on their optical and electrochemical properties. These dyes were successfully synthesized by Stille coupling reactions using 3-stannylcyclobutenediones and brominated NDI derivative, followed by a condensation reaction. DFT calculation predicts that the present dyes adopt distorted structures coming from a steric hindrance between semisquaraine and NDI moieties. The hybrid dyes show low-lying LUMOs due to the introduction of electron-deficient NDI moiety and broad absorption spectra in the far-red region. The absorption spectra of their thin films were bathochromically shifted relative to those in solution, indicating that hybrid dyes formed J aggregates.     

Theoretical study on tetrazole and its derivatives (3) MP2 and thermodynamic calculations of amino derivatives of tetrazole

Fully optimized geometries and electronic structures of amino derivatives of tetrazole are obtained at MP2/6-31G* level. The tetrazole rings are planar and aromatic for all the amino derivatives of tetrazole. The amino group is not co-planar with the ring and its conformation is mainly determined by the lone pair electronic repulsion between the substituent and the ring. N(4) atom is more negatively charged and is the most probable coordination site. The energy gaps between LUMOs and HOMOs of 2H-aminotetrazoles and C-aminotetrazole neutrals are smaller than those of the corresponding 1H-isomers and N-aminotetrazole neutrals respectively. The IR frequencies, thermodynamic properties and temperature-dependent functions for heat capacities in the form (a bT cT2) in the 300-1000K range are reported.     

Synthesis and electroluminescent properties of naphthalimide derivatives

Naphthalimide derivatives, N-ethyl-4-acetylamino-l ,8-naphthalimide (EAAN) and polymer with N-propyl-4-acetylamino-l,8-naphthalimide (PAAN) side-chain (P-PAAN) were successfully synthesized. Electroluminescent devices of ITO/PVK(120nm)/EAAN(50nm)/Al(150nm) (Ⅰ) and ITO/PVK P-PAAN( 10:1) (50nm)/Al(150nm) (Ⅱ) constructed with EAAN and P-PAAN as the emitting layer were investigated, whereas the single-layer devices of ITO/EAAN or P-PAAN(50nm)/Al(l50nm) (Ⅲ) were not observed to have any e-mission light. The emission results revealed that the exciton recombination formed by positive and negative charge carriers injected from electrodes of devices Ⅰ and Ⅱ was much more balanced than that of devices Ⅲ, which implied that naphthalimide derivatives are a new type of electron-transporting materials with high performance. The electron-transporting properties of naphthalimide derivatives were also elucidated by investigation of the electroluminescent behaviors from both devices of ITO/PPV (80nm)/Al and ITO/P     

Effect of γ-irradiation and thermal annealing on the molecular–topological structure of a copolymer of tetrafluoroethylene and perfluoro(propyl vinyl ether)

The molecular–topological structure of a copolymer of tetrafluoroethylene and perfluoro(propyl vinyl ether) subjected to γ-irradiation and thermal annealing has been studied for the first time with the use of thermomechanical spectrometry. The pseudonetwork structure of the copolymer contains an amorphous block (interjunction chains) and crystalline segments (branching points). The diblock amorphous and crystalline structure with a crystal structure fraction of 0.21 transformed into an almost completely amorphous structure with a crystallite fraction of 0.06 after the irradiation of the copolymer at a dose of 600 kGy. Thermal annealing at 483 K formed a new structure: a high-temperature amorphous block.     

Synthesis and properties of fibers prepared from lactic acid–glycolic acid copolymer

A method for preparing laboratory samples of fibers from glycolide-co-D,L-lactide to produce bioresorbing suture filaments with a controlled complex of properties is developed. The morphology of fibers obtained through melt spinning is studied. The peculiarities of the mechanical properties of fibers are investigated.     

Mechanical properties and heat shrinkability of electron beam crosslinked polyethylene–octene copolymer

The mechanical properties and heat shrinkability of electron beam crosslinked polyethylene–octene copolymer were studied. It was found that gel content increases with increased radiation dose. The analysis of results by the Charlesby–Pinner equation revealed that crosslinking was dominant over chain scission upon irradiation. Formation of a crosslinked structure in the electron beam irradiated sample was confirmed by the presence of a plateau of dynamic storage modulus above the melting point of the polymer. Wide-angle X-ray diffraction revealed that there was little change in crystallinity for the irradiated samples, indicating that radiation crosslinking occurs in the amorphous region of the polymer. The tensile modulus increases, whereas the elongation at break decreases with increased radiation dose. The heat shrinkability of the material increased with an increased radiation dose because the radiation-induced crosslinks serve as memory points during the shrinking process.     

Preparation and properties of copolymer resins based on phenolphthalein benzoxazine–benzoic acid and bisoxazoline

The novel phenolphthalein benzoxazine–benzoic acid (PBB) was synthesized. The structure of the monomer was supported by FTIR, ¹H-NMR, and elemental analysis. The curing behavior of PBB–bisoxazoline (1,3-PBO) resin was monitored by FTIR and differential scanning calorimetry. It was found that PBB–bisoxazoline resin exhibited two-stage polymerization mechanism. The thermogravimetry showed that PBB–bisoxazoline resin had good heat resistance due to the rigidity of PBB polymer chains and the high cross-linking density of copolymer. Furthermore, it seemed that the reaction between PBB and 1,3-PBO also led to an additional cross-linking, which increased the cross-linking density and delayed the decomposition. The cured resin had low water absorption.     

Preparation of monodispersed vinylpyridine–divinylbenzene porous copolymer resins and their application to high-performance liquid chromatographic separation of aromatic amines

For the separation of aromatic amines, two types of monodispersed porous polymer resins were prepared by the copolymerization of 2-vinylpyridine and 4-vinylpyridine with divinylbenzene in the presence of template silica gel particles (particle size 5 μm), followed by dissolution of the template silica gel in an alkaline solution. The transmission electron micrographs and the scanning electron micrograph revealed that these templated polymer resins have a spherical morphology with a good monodispersity and porous structure. Using these monodispersed polymer resins, the high-performance liquid chromatographic separation of aromatic amines in the mobile phases of pHs 2.0, 2.9, 4.1, 7.2 and 11.7 were carried out. The 2-vinylpyridine–divinylbenzene copolymer resins showed slightly stronger retentions for aromatic amines than the 4-vinylpyridine–divinylbenzene copolymer resins. Under acidic conditions (around pH 2.0), aniline and the toluidines showed no retention on these copolymer resins due to the repulsion between the cationic forms of these amines and pyridinium cations in the stationary phase, whereas less basic aromatic amines or non-basic acetanilide showed slight retentions. Above pH 4.1, the separation of aromatic amines with these polymer resins showed a typical reversed-phase mode separation. Therefore, the separation patterns of aromatic amines are effectively tunable by changing the pH value of the mobile phases. A good separation of eight aromatic amines was achieved at pH 2.9 using the 2-vinylpyridine–divinylbenzene copolymer resins.     

Studies on high-temperature thermal transformation and dielectric property of aluminum–chromium phosphates

High-temperature thermal transformation of aluminum–chromium phosphates has been investigated by means of DSC–TG, IR, and XRD analysis. The relative dielectric constant and thermal decomposition were measured and discussed. The results show that crystallization and thermal decomposition started at about 1,273 K, only AlPO₄ and Cr₂O₃ have been found at 1,873 K due to the decomposition of PO ₃ ^? , P₂O ₇ ^2? , and PO ₄ ^3? . The relative dielectric constant is fluctuant.     

Study of microstructure and thermal properties of the low-melting Bi–In eutectic alloys

Journal of Thermal Analysis and Calorimetry - This study reports the results of microstructure and thermal analysis of low-melting Bi–In alloys with potential for commercial application in...