Study on dynamic interfacial tension of 3-dodecyloxy-2-hydroxypropyl trimethyl ammonium bromide at liquid/liquid interface

Dynamic interfacial tension between aqueous solutions of 3-dodecyloxy-2-hydroxypropyl trimethyl ammonium bromide (R₁₂HTAB) and n-hexane were measured using the spinning drop method. The effects of the R₁₂HTAB concentration (the concentration below the CMC) and temperature on the dynamic interfacial tension have been investigated; the reason of the change of dynamic interfacial tension with time has been discussed. The effective diffusion coefficient, D_a, and the adsorption barrier, _a, have been obtained from the experimental data using the extended Word–Tordai equation. The results show that the dynamic interfacial tension becomes smaller while _a becomes higher with increasing R₁₂HTAB concentration in the bulk aqueous phase. D_a decreases from 5.56 × 10⁻¹² m⁻² s⁻¹ to 0.87 × 10⁻¹² m⁻² s⁻¹ while _a increases from 5.41 kJ mol⁻¹ to 7.74 kJ mol⁻¹ with the increase of concentration in the bulk solution of R₁₂HTAB from 0.5 × 10⁻³ mol dm⁻³ to 4 × 10⁻³ mol dm⁻³. Change of temperature affects the adsorption rate through altering D_a and _a. The value of D_a increases from 5.56 × 10⁻¹² m⁻² s⁻¹ to 13.98 × 10⁻¹² m⁻² s⁻¹ while that of _a decreases from 5.41 kJ mol⁻¹ to 5.07 kJ mol⁻¹ with temperature ascending from 303 K to 323 K. The adsorption of surfactant from the bulk phase into the interface follows a mixed diffusion–activation mechanism, which has been discussed in the light of interaction between surfactant molecules, diffusion and thermo-motion of molecules.     

Effect of magnetostrictive phase on structural, dielectric and electrical properties of NiFe2O4 + Pb0.93La0.07(Zr0.60Ti0.40)O3 composites

Particulate composites of NiFe₂O₄ (NFO) and Pb_0.93La_0.07 (Zr_0.60Ti_0.40) O₃ (PLZT) were synthesized by solid-state reaction technique. Structure and surface morphological studies were carried out using X-ray diffraction and scanning electron microscopy techniques, respectively. Frequency dependent variation of dielectric constant (), loss tangent (tan δ) and ac resistivity for (x) NFO + (1−x) PLZT composites in the range 100 Hz–5 MHz at room temperature were studied. The temperature dependence of dielectric constant (′), loss tangent (tan δ) was studied in wide temperature range of measurement at fixed frequencies. Also DC resistivity measurements were carried out in the temperature range of 300 K–923 K. Structural, dielectric and electrical properties show notable change due to presence of magnetostrictive NFO phase along with PLZT.     

Pyrolysis of poly(phenylene vinylene)s with polycaprolactone side chains

The thermal degradation characteristics of a new macromonomer poly(-caprolactone) with central 4,4′-dicarbaldehyde terphenyl moieties and poly(phenylene vinylene)s with well defined (-caprolactone), (PPV/PCL) as lateral substituents were investigated via direct pyrolysis mass spectrometry. The unexpectedly high thermal stability of the macromonomer was attributed to intermolecular acetylation of benzaldehyde yielding a hemiacetal and causing a crosslinked structure during the pyrolysis. Increased thermal stability of the PCL chains was detected for all samples. The increase in stability of PCL chains was much more pronounced than was detected for poly(p-phenylene)-graft-poly(-caprolactone) copolymer (PPP/PCL); the upward temperature shift was about 100 °C for PPV/PCL and only 20 °C for PPP/CL. This pronounced effect may be due to higher thermal stability of PPV compared to PPP and the decrease in steric hindrance for PPV with PCL side chains.     

Interrupted thermal desorption of TiH2

Structural changes of commercial TiH₂ were studied using interrupted temperature desorption spectroscopy and X-ray diffraction techniques to understand the mechanism of its degradation under non-equilibrium conditions. Rapid cooling on different stages of temperature-programmed heating allowed to study the intermediate phase compositions that evolve upon cooling from the high-temperature phase βTi(H). The phase transformation sequence is described as a number of consecutive reactions corresponding to the observed desorption peaks. Phases δTiH_2−x, γTiH, and the solid solution αTi(H) were found to be intermediates in the TiH₂ → αTi transformation when the latter is interrupted. Additional evidence for the thermodynamic stability of γTiH is given.     

The electronic states of but-2-yne studied by VUV absorption, near-threshold electron energy-loss spectroscopy and ab initio configuration interaction methods

The photoabsorption spectrum of but-2-yne in the range 5.5–11 eV (225–110 nm) has been recorded using a synchrotron radiation source. The spectrum is dominated by three d-type Rydberg series, converging to the first ionisation energy (IE) (π⁻¹, 9.562 eV). Origins of the π3d members are 7.841, 7.977 and 8.018 eV, respectively. Transitions of low intensity, arising from excitation of the π3s state (origin, 6.35 eV) and two π3p Rydberg states (7.38 and 7.51 eV, respectively) have also been identified in the spectrum. Near-threshold electron energy-loss spectra reveal valence excited triplet states at about 5.2 and 5.8 eV, respectively.Electronic excitation energies for valence and Rydberg-type states have been computed using ab initio multi-reference multi-root CI methods. These studies used a triple zeta + polarisation basis set, augmented by diffuse (Rydberg) orbitals, to generate the theoretical singlet and triplet energy manifolds. The correlation of theory and experiment shows the nature of the more intense Rydberg state types, and identification of the main valence and Rydberg bands. Calculated energies for Rydberg states are close to those expected, and there is generally a good correlation between the theoretical and experimental envelopes. It was possible to generate singlet Rydberg states which relate to the 5-lowest IEs of but-2-yne; furthermore, the separation of these sequences shows that the IE order (under D_3h symmetry) is: , also supported by direct calculation of the IEs by CI.The lowest valence singlet states are ππ^*, optically forbidden, and calculated to lie near 7.3 and 7.6 eV. The states which contribute strongly to the observed spectrum are πσ^* near 7.9 eV having excitation, followed by several ππ^* and πσ^* states between 10.0 and 10.5 eV; an ¹E′ antisymmetric combination(2e′2e″ − 2e′2e″) is by far the strongest in intensity. A further group of symmetry-allowed valence states are calculated to lie near 12.3 and 12.9 eV. The two lowest triplet states, both of E′ symmetry (ππ^*), have vertical excitation energies of 5.7 and 6.2 eV, but are strongly bent with a trans-CCCC unit (C_S and C_2h). The theoretical work confirms that, on intensity grounds, valence excited states do not contribute significantly to the spectrum. CI calculations of the ionic states give the ionisation energy sequence (D_3h): . Adiabatic structures for the first cation, two triplets, and a singlet (C_2h) were obtained; these show shortening of C–C, and lengthening of CC, in a trans-CCCC, as is found with ethyne.     

Equilibrium constants of some protonated,nonprotonated and hydroxo complexes of uranium(VI) with xylenol orange

Summary The species, UO₂H₃L^–, UO₂H₂L^2–, UO₂HL^3–, UO₂L^4–, UO₂(OH)L^5– and UO₂(OH)₂L^6– are found in the equilibria between uranyl ions and 3,3-bis[N,N-di(carboxymethyl)-aminomethyl]-o-cresolsulphonphthalein (H₆L; xylenol orange; dcac) in aqueous solution. The equilibria have been studied by the potentiometric method at 25° and at an ionic strength of 0.1M (KNO₃). New algebraic equations have been employed to evaluate the equilibrium constants.     

Monomer insertion mechanism of ring-opening polymerization of -caprolactone with yttrium alkoxide intermediate: A DFT study

The mechanism of -caprolactone (CL) insertion into a Y–OCH₃ bond was investigated using density functional theory (DFT) calculations. The optimized geometries and corresponding Gibbs-free energies of the intermediates were obtained, which confirmed a four-step coordination-insertion mechanism. The coordination of CL onto yttrium center led to a nucleophilic addition of the carbonyl group of CL, followed by an intramolecular alkoxide ligand exchange. A monomer insertion was completed by the CL ring opening via acyl–oxygen bond cleavage. The formation of the five-coordinated yttrium intermediate, 3, was found to be the rate-determining step. This study could be applicable to ring-opening polymerisation (ROP) of CL initiated by lanthanide metal complexes.     

Thermochemistry of heteroatomic compounds

The enthalpies of combustion (H _comb) of 13 primary, secondary, and tertiary alkylphoshines in the condensed state were calculated using the equation H _comb = –860.7 – 107.0N, where N is the number of valent (bond-forming) electrons. This equation can be used for the calculation of enthalpies of combustion and formation of phosphoric acid esters.Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1693–1694, August, 2004.     

Determination of antioxidant capacities of vegetable oils by ferric-ion spectrophotometric methods

Two ferric-ion-based total antioxidant capacity methods: 1,10-phenanthroline (Phen) and ferric reducing antioxidant power (FRAP) were used for determination of antioxidant capacities (AC) of the acetonic and methanolic extracts of vegetable oils. The obtained mean Phen and FRAP values for acetonic extracts of olive oils, rapeseed, rice and four sunflower oils (39.3–336.5 and 39.5–339.6 μmol Fe/100 g) were higher than for methanolic extracts (22.8–307.3 and 23.5–300.1 μmol Fe/100 g). However, antioxidant capacities of methanolic extracts of corn oil, blended oils and two sunflower oils with garden green flowers (56.5–312.9 and 53.9–306.5 μmol Fe/100 g for Phen and FRAP methods, respectively) were higher than for acetonic extracts of these oils (54.2–249.2 and 52.9–244.7 μmol Fe/100 g for Phen and FRAP methods, respectively). There is a linear and significant correlation between these two analytical methods (r = 0.9989 and 0.9986 for acetonic and methanolic extracts). Also, total phenolic compounds (TPC) in the studied oils correlated with their antioxidant capacities determined by Phen and FRAP methods (r = 0.9012, 0.7818 and 0.8947, 0.7830 for acetonic and methanolic extracts, respectively). The comparable precision (R.S.D. = 0.8–4.6%, 0.9–4.9% and 0.7–4.0%, 0.6–4.0% for acetonic and methanolic extracts, respectively) and sensitivity ( = 1.27 × 10⁴, 1.11 × 10⁴ and 2.62 × 10⁴ dm³ mol⁻¹ cm⁻¹) for the proposed Phen and the modified FRAP methods, demonstrate the benefit of the Phen method in the routine analysis of antioxidant capacities of vegetable oils.     

An improved perturbed hard-sphere equation of state

The Carnahan–Starling–Patel–Teja (CSPT) equation of state was revisited to improve the fitting accuracy of vapour–liquid equilibrium data of pure fluid substances. By setting the pseudo-critical compressibility factor and the correction coefficient in the attractive parameter as the temperature-dependent variables, the fitting accuracies of the vapour pressures and the saturated liquid-phase densities from the new CSPT increased significantly compared with the Patel–Teja equation of state (PT) and the Peng–Robinson equation of state (PR) and the original CSPT model. The new CSPT combined with temperature-dependent functions was applied to the vapour–liquid equilibrium data available for 45 pure substances. The results indicate that the new CSPT model can accurately reproduce the experimental vapour–liquid equilibria in the whole temperature and pressure range. The successful calculations of the PVT in the critical region suggest the new CSPT has wide applicability. The new CSPT model is also superior to PR and the original CSPT for calculating the phase behaviour of binary mixtures.     

A perturbed hard-sphere-chain equation of state for nematic liquid crystals and their mixtures with polymers

A perturbed hard-sphere-chain (PHSC) equation of state is presented to compute nematicisotropic equilibria for thermotropic liquid crystals, including mixtures. The equation of state consists of an isotropic term and an anisotropic term given by the Maier-Saupe theory whose contribution disappears in the isotropic phase. The isotropic contribution is the recently presented PHSC equation of state for normal fluids and polymers which uses a reference equation of state for athermal hard-sphere chains and a perturbation theory for the squarewell fluid of variable well width. The PHSC equation of state gives excellent correlations of pure-component pressure-volume-temperature data in the isotropic region and, combined with the Maier-Saupe theory, correlates the dependence of nematic-isotropic transition temperature on the pressure. Theory also predicts a nematic-isotropic biphasic region and liquid-liquid phase separation in a temperature-composition diagram of binary mixtures containing a nematic liquid crystal and a normal fluid or polymer. Theory and experiment show good agreement for pure fluids as well as for mixtures.     

Phase controllable synthesis of unusual -Ga2O3 single crystals with promising luminescence property

A new synthetic approach to unusual -Ga₂O₃ with improved luminescence properties was developed by taking advantage of a microwave-assisted synthesis followed by calcinations at appropriate temperatures. Upon control of crystallinities of GaOOH precursors and the followed calcination temperature, the single crystalline -Ga₂O₃ nanorods can be synthesized in a large scale. The resulting products were characterized by transmission electron microscopy, powder X-ray diffraction, and cathodoluminescence. The luminescence property of this unusual Ga₂O₃ phase was investigated for the first time.     

Synthesis and optical behaviors of 2-(9-phenanthrenyl)-, 2-(9-anthryl)-, and 2-(1-pyrenyl)-1-alkylimidazole homologues

Eight 2-(9-phenanthrenyl)-, 2-(9-anthryl)- and 2-(1-pyrenyl)-1-alkyl-benzimidazole compounds, three 2-(9-anthryl)-1-alkylphenanthroimidazole compounds and five 4,5-diphenyl-1-alkyl-2-(9-anthryl)imidazole compounds were synthesized by alkylation reactions of the corresponding benzimidazole, phenanthroimidazole or imidazole compounds. 2-(10-Bromo-9-anthryl)-1-alkyl-benzimidazole compounds were prepared by bromination reaction of 2-(9-anthryl)-1-alkylbenzimidazole compounds. All the synthesized compounds were characterized by elemental analysis, ¹H NMR, ¹³C NMR, MS or HRMS; their absorption coefficients (), maximum absorption λ_amax, fluorescence emission maximum λ_em, Stokes shifts and fluorescence quantum yields (Φ_F) in ethyl acetate were determined; their fluorescent lifetimes (T₁ and T₂) were measured in ethyl acetate and in solid state, respectively. The crystal structure of 2-(9-anthryl)-1-n-butyl-4,5-diphenylimidazole (12a) was determined to be triclinic, space group P-1 types, using single crystal X-ray crystallography technique. The results showed that these compounds exhibited moderate fluorescence-emission abilities and higher solubility in most organic solvents than their corresponding starting materials. The relationships between the optical behaviors and structures for these compounds were discussed.     

Gas-Phase NMR Spectroscopy

The Murnaghan-Hildebrand equation of state, an accurate equation of state for many solids and liquids, is introduced for use in the illustration of thermodynamic relationships. It is shown to meet the need for an equation of state accurate over a wide range of pressures. Parameters are given for four solid phases of iron and for the liquid, with which eleven thermodynamic functions including V, U, H, S, V, V/B, and G can be calculated at any specified temperature and pressure. The program for these calculations can be used to represent experimental values, to illustrate thermodynamic relationships, to calculate chemical and phase equilibria, and to stimulate student interest from the study of real systems, for instance, the form of iron in the core of the earth.     

Boron trifluoride-catalyzed degradation of poly--caprolactone at ambient temperature

Poly--caprolactone (PCL) can be accelerated to degrade in the presence of boron trifluoride at ambient temperature. The degradation behaviors were studied by using the inherent viscosity measurement, gel permeation chromatography (GPC), infrared analysis (FTIR), nuclear magnetic resonance analysis (NMR), and thermal analysis (DSC). With increasing the addition amount of boron trifluoride, the molecular weight of PCL decreases; the molecular weight distribution is broadened; and the degree of crystallinity of PCL increases at first at low BF₃ level, then decreases when BF₃ content exceeds to 2.64 wt%. The results of IR, ¹HNMR and GPC reveal that -caprolactone monomer does not occur and the main degradation products are the oligomers of PCL with low molecular weight. The mechanism for boron trifluoride-catalyzed degradation of PCL is discussed.     

Analysis of {[N,N-dialkylamide or 1-methyl-2-pyrrolidone] + 1-chloroalkane or α,ω-dichloroalkane} mixtures in terms of group contribution

The experimental vapour–liquid equilibria, VLE, excess molar Gibbs energies, , and excess molar enthalpies, , determined previously for the systems N,N-dimethylformamide, or N,N-dimethylacetamide, or 1-methyl-2-pyrrolidone + 1-chlorobutane, or +1-chlorohexane, or +1-chlorooctane, or +1,2-dichloroethane, or +1,4-dichlorobutane, or +1,6-dichlorohexane, are examined using the DISQUAC group contribution model. The dispersive and quasi-chemical interchange parameters for the contacts chloro-amide in the mixtures with N,N-dialkylamide or 1-methyl-2-pyrrolidone with chloro- or α,ω-dichloroalkane were calculated. The model reproduces quite well the experimental data.     

Rate and equilibrium constants of transfer of the dimethylcarbamoyl group between substituted pyridines and their N-oxides

Transfer of the dimethylcarbamoyl group from N-acyloxypyridinium salts to pyridines and from N-acylpyridinium salts to pyridine N-oxides was studied in acetonitrile. Equations relating the reaction rates and equilibria in the N-O and O-N acyl transfer series to the basicity of the nucleophile and leaving group were obtained. The reactions all are one-stage and occur by the forced concerted SN2 mechanism. The intersecting state model was used to obtain a modified Marcus equation that accounts for the asymmetry of the transition state with respect to reagents and products and allows uncontradictory analysis of the reaction mechanism.Translated from Zhurnal Obshchei Khimii, Vol. 74, No. 10, 2004, pp. 1720–1727.Original Russian Text Copyright © 2004 by Rybachenko, Shreder, Gokhfeld, Chotii, Kovalenko, Lenska.This revised version was published online in April 2005 with a corrected cover date.     

Effects of α-zirconium phosphate aspect ratio on the properties of polyvinyl alcohol nanocomposites

To study the effect of the aspect ratio (ratio of platelet length to thickness) of α-zirconium phosphate (α-ZrP) on the mechanical and thermal properties of polymer nanocomposites, polyvinyl alcohol (PVA)/α-zirconium phosphate (α-ZrP) nanocomposites with three distinctive aspect ratios at ca. 300, 590 and 1300 were prepared and characterized. Wide-angle X-ray diffraction (XRD), scanning electron microscopy (SEM), thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC), dynamic mechanical (DMA) and tensile testing were utilized to characterise the film properties. As expected, it was found that the storage modulus, tensile strength (σ_b), elongation at break (_b) and decomposition temperature increased as the α-ZrP aspect ratio increased from 300 to 590. However, when the aspect ratio reached 1300, the enormously enlarged specific surface area of α-ZrP resulted in strong aggregation of the nanolayers which resulted in severe deterioration of the film properties.     

Schrödinger Equation Solutions for the Central Field Power Potential Energy II. V(r) = −V 0(r/a 0)2ν−2, 0 ≤ ν ≤ 1, the Bound States

The bound states of the generalized Schrödinger equation system with radial potential energy V(r) = –V ₀(r/a ₀)^2–2, 0 1, are described. The solutions of the differential equation are related to the functions for the bound state problem with 1. The Green's function is constructed as well as its first iteration, the traces of both functions are calculated, and an upper and lower bound for the ground state is established. A WKB-like approximate solution for the eigenvalues and eigenfunctions is derived.     

Solid–liquid metastable equilibria in the quaternary system (NaCl–KCl–CaCl2–H2O) at 288.15 K

The solubilities and the physicochemical properties (densities, viscosities, refractive indices, conductivities, and pH) in the liquid–solid metastable system (NaCl–KCl–CaCl₂–H₂O) at 288.15 K have been studied using the isothermal evaporation method. Based on the experimental data, the dry-salt phase diagram, water-phase diagram and the diagram of physicochemical properties vs. composition in the system were plotted. The dry-salt phase diagram of the system includes one three-salt co-saturated point, three metastable solubility isotherm curves, and three crystallization regions corresponding to sodium chloride, potassium chloride and calcium chloride hexahydrate. Neither solid solution nor double salts were found. Based on the extended Harvie–Weare (HW) model and its temperature-dependent equation, the values of the Pitzer parameters β⁽⁰⁾, β⁽¹⁾, C for NaCl, KCl and CaCl₂, the mixed ion-interaction parameters θ_Na,K, θ_Na,Ca, θ_K,Ca, Ψ_Na,K,Cl, Ψ_Na,Ca,Cl, Ψ_K,Ca,Cl, the Debye–Hückel parameter A and the standard chemical potentials of the minerals in the quaternary system at 288.15 K were obtained. In addition, the average equilibrium constants of metastable equilibrium solids at the same temperature were obtained using a method derived from the activity product constant for the metastable system. Using the standard chemical potentials of the minerals and the average equilibrium constants of solids at equilibrium, the solubility predictions for the quaternary system are presented. A comparison between the calculated and experimental results shows that the predicted solubilities obtained with the extended HW model using the average equilibrium constants agree well with experimental data.