Electrical conductance of CHCl3 solutions of polyethylene oxide doped with KCI

CHCl3 solutions containing a few percent polyethylene oxide PEO (M_W = 200 000) or the low-molecular model dioxane are stirred at 50°C during more than 100 h in the presence of small amounts of KCl. The specific conductance, the viscosity and the density of the solutions are measured at 25°C as a function of time. Both PEO and dioxane act as ligands improving the solubility of KCl. The relaxation times are of the order of several hours. After 40 h or more the viscosity of the solutions increases in a spectacular way. However, the most striking observation is that the specific conductance of the polymeric solutions at 25°C is systematically 5% higher than the value measured with the same sample at 45°C, just as for metals. The effect of the dilution of the primary stirred solutions either in the pure solvent or in the initial polymer solution is investigated. These results are discussed in terms of a three-step mechanism in the polymer systems: (1) Loading of the coils to polymeric cations with a full elementary charge, as a consequence of charge transfer interactions of the crown-ether type with numerous K⁺ ions penetrating into the coils; (2) Electron tunnelling conduction of the Hamill—Ceulemans type from one positive coil to the neighbouring one; (3) Alteration of the structure of the coils and of their hydrodynamic radius by the motions of K⁺ in the coils. These ‘brachiation’ motions by a hopping mechanism result from an increased mobility of the complexed K⁺ ions, which is also the origin of the Zundel effect. They do not directly contribute to the conductance but are responsible for the delayed increase of the viscosity.     

Ion dissociation and conduction of Nafion/modified oligo(oxyethylene) composite films

In order to improve the ionic conductivity of solid polymer electrolyte by controlling ion(alkali metal ion)–dipole(ether oxygen) interaction, two kinds of modification were adopted on oligo(oxyethylene) (OOE). One is the capping of terminal hydroxyl groups of OOE with methyl or acetyl groups. The other is the replacement of the center ethylene group of OOE with methylene or propylene group. Ion–dipole interaction was analyzed by measuring the ion dissociation, ion conduction and T_g of Nafion/modified OOE composite films. The modification of the end groups was more effective than that of the center group in increasing ionic conductivity. The methyl group is superior to the acetyl group as the end group of OOE for lithium ion conduction.     

Viscosity behavior of polyelectrolyte copolymers containing sulfonate groups in mixed organic solvents

Copolymerization of 2-acrylamido-2-methylpropane sulfonic acid (AMPS, monomer 1) with 2-hydropropyl methacrylate (HPM, monomer 2) was conducted in ethylene glycol/water (1 : 1 in weight) at 70°C. The reactivity ratios estimated from the copolymer composition at low conversion are r₁ = 2.31 ± 0.25 and r₂ = 11.70 ± 1.05. The azeotropic composition was found at the monomer mole ratio AMPS/HPM equal to 8/2. Viscosity of these copolymers was measured in dimethyl sulfoxide (DMSO) and DMSO/tetrahydrofuran (THF) mixed solvent at 25 ± 0.05°C. Polyelectrolyte behavior was observed for all the copolymers, even in the mixed solvent containing 65 wt % of THF. The reduced viscosity at constant polymer concentration decreased with increasing THF content in the mixed solvent. The copolymers having AMPS repeat units more than 42 mol % precipitated in the mixed solvent when the THF was beyond 68 wt %. The viscosity reduction and precipitation in the copolymer solutions with increasing THF can be attributed to the dipole–dipole attraction between ion-pairs formed in less-polar medium. This is helpful in understanding the volume phase transition in highly charged hydrogels caused by mixing solvents. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35 : 1433–1438, 1997     

Composition and electrochemical properties of LiCu xMn 2- xO 4 and LiCu 0.5- yAl yMn 1.5O 4

In order to gain a better understanding of the parameters affecting the capacity and performance of spinel electrode materials, the chemical composition and cation distribution of three members of the LiCu_xMn_2–xO₄ and LiCu_0.5–yAl_yMn_1.5O₄ series have been studied by chemical analysis, X-ray diffraction and X-ray absorption spectroscopy. The synthesis used stoichiometric and lithium-excess precursors. The results evidence that lithium is always incorporated in lower contents than expected from the nominal stoichiometry, owing to the occurrence of significant amounts of copper in the tetrahedral sites of the structure. Manganese displays an oxidation state below 4+ in all these solids, while the lithium-excess synthesis leads to a slightly higher average oxidation state. The electrochemical results evidence the lack of improvement in capacity by using lithium-excess synthesis, while a significant increase in capacity is obtained by aluminium doping, reaching values of 100 mAh/g.     

Formation of copper oxide through NaNO3–KNO3 eutectic melt and its catalytic activity in the decomposition of ammonium perchlorate

The decomposition of basic copper carbonate in the presence and absence of NaNO₃–KNO₃ eutectic melt has been studied by employing isothermal TG and dynamic TG/DSC techniques. The rate constants for the decomposition in the presence of eutectic melt were found to be higher than when carbonate was heated alone. In both the cases copper oxide was found to be the end product. Catalytic activity of copper oxide obtained by the two methods were tested for the decomposition of ammonium perchlorate.     

Construction of ternary phase diagrams in nonsolvent/solvent/PMMA systems

In this work, the ternary phase diagrams in three nonsolvent/solvent/PMMA systems (n-hexane/n-butyl acetate/PMMA, water/acetone/PMMA, and n-hexane/acetone/PMMA) were constructed by theoretical calculation and experimental measurement. Binodal curves were calculated by using the Flory–Huggins theory for three-component systems and measured by titrating the PMMA solution with nonsolvent until the onset of turbidity. By using concentration-dependent nonsolvent/solvent and solvent/PMMA interaction parameters and constant nonsolvent/PMMA interaction parameters, good agreement has been obtained between the calculation and the measurement. The values of nonsolvent/solvent interaction parameters were taken from the literature sources, and the values of solvent/PMMA and nonsolvent/PMMA interaction parameters were measured by vapor sorption and swelling equilibrium, respectively. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 607–615, 1998     

Synthesis and thermoresponsive properties of OEGylated polypeptide with a LCST at body temperature in water and with a UCST in alcohol or ethanol/water solvent mixture

Thermoresponsive polypeptides bearing oligo(ethylene glycol) (OEG) pendants (i.e., P1‐OEG_x and P2‐OEG_x, x = 3, 7) were synthesized by copper‐mediated 1,3‐dipolar cycloaddition with high grafting efficiency (≥97%) between side‐chain “clickable” polypeptides, namely poly(γ‐4‐(propargoxycarbonyl)benzyl‐l ‐glutamate) (P1) or poly(γ‐4‐(4‐propargoxyphenoxycarbonyl)benzyl‐l ‐glutamate) (P2) and azido functionalized OEG (N₃‐OEG_x). P1 and P2 with similar degree of polymerization (DP = 35 or 37) were prepared from triethylamine initiated ring‐opening polymerization of respective N‐carboxyanhydrides. P1‐OEG_x (x = 3, 7) and P2‐OEG₇ showed reversible UCST‐type phase transitions in various alcoholic solvents (e.g., ethanol, propanol, n‐butanol, and n‐pentanol). P2‐OEG₃ also showed reversible UCST‐type phase transitions in ethanol/water solvent mixtures at the weight percentage of ethanol no less than 50 wt %. P1‐OEG₇ and P2‐OEG₇ showed reversible LCST‐type phase transitions in aqueous solutions. Variable‐temperature UV–vis spectroscopy revealed that the LCST‐type phase transition temperature (T_pt) of P2‐OEG₇ with benzoic acid phenyl ester linkages was at around body temperature and it was barely changed with the variation of polymer concentration, yet it showed noticeable dependence on the nature of salt (i.e., NaCl, NaBr, NaI, or KCl) and salt concentration in the range of 0–300 mM. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 163–173     

Enhanced photocatalytic activity of Eu2O3/Ta2O5 mixed oxides on degradation of rhodamine B and 4-nitrophenol

Europium oxide/tantalum pentoxide (Eu₂O₃/Ta₂O₅) mixed oxides with different Eu₂O₃ dopings were prepared by a single-step sol–gel process via hydrolysis of tantalum pentachloride in the presence of europium nitrate. The products were in the amorphous and orthorhombic phase structures, respectively, based on the different calcination temperatures (200 and 500 °C). Composition, morphology, phase structure, Eu₂O₃-doping mode in the Ta₂O₅ matrix and optical absorption property of the products were characterized by inductively coupled plasma atomic emission spectroscopy (ICP-AES), field emission scanning electron microscopy (FESEM), X-ray diffraction patterns (XRD), X-ray photoelectron spectroscopy (XPS) and UV–vis diffuse reflectance spectroscopy (UV–vis/DRS). The UV-light photocatalytic activity of the products was evaluated by degradation of aqueous rhodamine B (RB) and 4-nitrophenol (4-NP). The results showed that the photocatalytic activity of as-prepared Eu₂O₃/Ta₂O₅ was higher than that of pure Ta₂O₅ regardless of their phase structures. Among the tested samples, Eu₂O₃/Ta₂O₅ with 0.49% Eu loading obtained with 200 °C exhibited the highest activity to degradation of the above two model molecules. The reasons of this enhanced photocatalytic activity were discussed.     

Solid–liquid equilibrium of K2SO4 in solvent mixtures at different temperatures

The objective of the present work is to represent the solid–liquid equilibrium of potassium sulfate in diverse water + organic solvent mixtures. This representation is carried out between 288.15 and 318.15 K in the following solvent mixtures: water + 1-propanol, water + methanol, water + ethanol and water + acetone. The experimental solubility data of the potassium sulfate in the diverse mixed solvents were obtained from literature, and the thermodynamic representation of the phase equilibrium is based on a simple methodology reported in the literature. Good agreements are observed between the results obtained in this work and the experimental solubility data of K₂SO₄ in the different solvent mixtures.Since these systems present a notable decrease in solubility owing to the effect of the cosolvent, making them potentially suitable for separating potassium sulfate by drowning-out the crystallization process, the amounts of salt precipitated, as a function of the weight percent of cosolvent, was calculated for the four systems analyzed. In addition, the optimum yield was estimated as function of the mass fraction of 1-propanol for the K₂SO₄ + water + 1-propanol system.     

Deposition of gallium oxide nanodots prepared from metal‐assembling dendrimer molecules isolated by the spacing of the nonmetal‐assembling dendrimer molecules in the two‐dendrimers mixture monolayer

Phenylazomethine dendrimers (DPA) can precisely incorporate metal chlorides onto the imine sites in a stepwise fashion. Such precise dendrimer–metal complexes allow the preparation of size‐controlled subnanometer metal particles. We now propose a novel approach for the fabrication of size‐controlled subnanometer metal oxide dots isolated on a substrate using two different‐type dendrimers. One is a fourth‐generation phenylazomethine dendrimer (DPAG4) and the other is a benzylether dendrimer (BzEG3) with a zinc porphyrin core. Even though the diameter of BzEG3 corresponds to that of DPAG4, BzEG3 has no metal‐complexing site. Upon dip coating on a highly oriented pyrolytic graphite substrate by the mixed solution of the metal chloride‐assembling DPAG4 molecules and BzEG3 molecules, the dendrimer monolayer was immobilized on the substrate. The concentration of the dendrimer mixture was determined in order to separate each DPAG4–metal chloride complex molecule by BzEG3. Monodispersed metaloxide nanodot arrays could be obtained from the dendrimer monolayer in which DPAG4–metal chloride complex molecule is well isolated by the BzEG3 as a spacer after the hydrolysis of metal chlorides followed by the complete removal of dendrimers. Copyright © 2013 John Wiley & Sons, Ltd.     

Influence of the support on the state of nickel in the Ni/SiO2, Ni/ZrO2, and Ni/SO4/ZrO2 oxide systems studied by diffuse-reflectance IR spectroscopy

The Ni/SiO₂, Ni/ZrO₂, and Ni/SO₄/ZrO₂ systems were studied by diffuse-reflectance IR spectroscopy using CO as a probe molecule. The Ni/SiO₂ and Ni/ZrO₂ systems are similar in properties, and the state of nickel in the Ni/ZrO₂ system is determined by the specific surface area. In the Ni/SO₄/ZrO₂ system, the surface sulfur compounds affect substantially the state of nickel: Ni^δ+ species with a partial positive charge are formed due to the strong electron-acceptor properties of the sulfur compounds. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 409–413, March, 1998.     

Dispersity of stratum corneum in the mixed aqueous solutions of binary mixtures between N,N-dimethyldodecylamine oxide and sodium dodecyl sulfate or two terpenes

Solubilization of cholesterol, differential scanning calorimetric (DSC), nuclear magnetic resonance (NMR) and dynamic light scattering (DLS) measurements were performed in order to reveal the dispersion mechanisms of stratum corneum (SC) into each intact corneocytes in the following systems: (1) in the aqueous mixed solutions of sodium dodecyl sulfate (SDS) and N,N-dimethyldodecylamine oxide (C₁₂DMAO); (2) in the aqueous micellar solutions of C₁₂DMAO containing solubilized α-terpineol (α-T); and (3) in the aqueous micellar solutions of C₁₂DMAO containing solubilized limonene. The intercellular lamellar structure of SC was revealed to be disrupted and/or removed in all these solutions. However, considering the micellar sizes and the interaction among molecules in micelle, the dispersion mechanisms in these three systems were different each other. The three dispersion mechanisms of SC were estimated and discussed on the basis of the results of solubilization, DSC, NMR and DLS, respectively.     

A sensitive LC–MS/MS method for simultaneous determination of cabozantinib and its metabolite cabozantinib N‐oxide in rat plasma and its application in a pharmacokinetic study

Cabozantinib (CBZ) is used for the treatment of progressive, metastatic medullary thyroid cancer. Its major oxidative metabolite is cabozantinib N‐oxide (CBN), which contains a structural alert associated with mutagenicity, yet the pharmacokinetics studies lack the simultaneous investigation of CBN and dose proportionality. In the current study a simple LC–MS/MS method was developed and validated for the simultaneous estimation and pharmacokinetic investigation of CBZ and CBN in rat plasma. The analytes were separated on a Waters Atlantics C₁₈ column (2.1 × 150 mm, 3 μm). The mass spectrometry analysis was conducted in positive ionization mode with multiple reaction monitoring. Good linearity was observed over the concentration ranges of 0.500–5000 ng/mL for CBZ and 0.525–2100 ng/mL for CBN. The extraction recoveries were constant and the intra‐ and inter‐batch precision and accuracy were acceptable for the analysis of biological samples. The method was successfully applied for the simultaneous estimation of CBZ and CBN in a pharmacokinetic study in Sprague–Dawley rats. After oral administration of CBZ (1, 5 and 12.6 mg/kg), although CBZ showed dose proportionality, the metabolite CBN showed obvious nonlinear elimination pharmacokinetics with greater than dose‐proportional increases in exposure.     

Enthalpies of solvation of ethylene oxide oligomers CH3O(CH2CH2O)nCH3 (n = 1 to 4) in different H-bonding solvents: Methanol, chloroform, and water. Group contribution method as applied to the polar oligomers

The enthalpies of solution and solvation of ethylene oxide oligomers CH₃O(CH₂CH₂O)_nCH₃ (n = 1 to 4) in methanol and chloroform have been determined from calorimetric measurements at T = 298.15 K. The enthalpic coefficients of pairwise solute–solute interaction for methanol solutions have been calculated. The enthalpic characteristics of the oligomers in methanol, chloroform, water and tetrachloromethane have been compared. The hydrogen bonding of the oligomers with chloroform and water molecules is exhibited in the values of solvation enthalpy and coefficient of solute–solute interaction. This effect is not observed for methanol solvent. The thermochemical data evidence an existence of multi-centred hydrogen bonds in associates of polyethers with the solvent molecules. Enthalpies of hydrogen bonding of the oligomers with chloroform and water have been estimated. The additivity scheme has been developed to describe the enthalpies of solvation of ethylene oxide oligomers, unbranched monoethers and n-alkanes in chloroform, methanol, water, and tetrachloromethane. The correction parameters for contribution of repeated polar groups and correction term for methoxy-compounds have been introduced. The obtained group contributions permit to describe the enthalpies of solvation of unbranched monoethers and ethylene oxide oligomers in the solvents with standard deviation up to 0.6 kJ · mol⁻¹. The values of group contributions and corrections are strongly influenced by solvent properties.     

Comments on “The use of MoO3 and NiO (pure or mixed) oxide catalysts in the decomposition of KMnO4” by S.A. Halawy and M.A. Mohamed

The recent paper by Halawy and Mohamed [S.A. Halawy, M.A. Mohamed, Thermochim. Acta 345 (2000) 157] has raised several problems which need to be resolved. Our comments are given under the headings of the sections of the original paper.