Effect of PVC on low-polar isobutylene polymerization in the presence of BCl3

Summary The isobutylene polymerizations in the presence of BCl₃ were carried out in dichloromethane ([M]=7 mol/l) at-20°C in the presence and absence of PVC. The products of polymerizations in the absence of PVC are oligoisobutylenes with a narrow molecular weight distribution ; their structure was analyzed by ¹H-NMR spectroscopy. In addition to the signals assigned to known unsaturated terminal structures [ 4.62 and 4.82-CH₂C(CH₃)=CH₂, 5.12-CH=C(CH₃)₂], a new intense signal was found at 5.09 ppm and assigned to the structure-CH=C(CH₃)CH₂CH₃. A mixture of isobutylene homopolymers and PVC grafted with isobutylene (approx. 9.5% wt. isobutylene grafted) is formed in the presence of PVC.     

The Polymerization of Metal-Containing Vinylic Monomers of Iron and Tungsten with Metal–Carbon σ Bonds

A series of metal-containing vinylic monomers of the type and was homopolymerized using 2,2-azobisisobutyronitrile (AIBN) as the free-radical initiator. These monomers were also copolymerized with styrene in the presence of AIBN. These compounds represent a class of organometallic polymers in which the metal is bonded to the polymer backbone via a metal–carbon bond. The new compounds were characterized by IR and ¹H NMR spectroscopy as well as scanning electron microscopy, gel permeation chromatography, and thermoanalytical studies (DSC and TGA). The properties of the new organometallic polymers are discussed.     

Positive polyacetylene electrodes in aqueous electrolytes

Polyacetylene films, contacted with platinum mesh, have been polarized anodically in aqueous H₂SO₄, HClO₄, HBF₄ and H₂F₂ of medium concentrations (30–70 wt%). Two oxidation peaks are observed, the equivalents of which are 1 $${\text{(1) 0}}{\text{.045 F mol}}^{ - {\text{1}}} {\text{ CH (2) 0}}{\text{.23 F mol}}^{ - {\text{1}}} {\text{ CH}}$$ The potential of the Process 1 decreases linearly with increasing acid concentration by 20–40 mV mol^?1 dm^?3, while the potential of Peak 2 exhibits normal Nernst behaviour (about + 60 mV decade^?1. Process 1 is partially reversible, while Process 2 is totally irreversible. From these findings for Process 1 we conclude the reversible insertion of anions into the polyacetylene host lattice, which is primarily oxidized to the polyradical cation, with the co-insertion of acid molecules HA to yield the insertion compound [(CH)⁺·yA^?·vyHA] _x y?4.5% andv=1.5 for H₂SO₄ and HClO₄. In the course of Process 2, the polymer is irreversibly oxidized according to $$( - ^ \cdot {\text{CH}} \cdot \cdot \cdot \cdot \cdot \cdot \cdot \cdot ^ \oplus {\text{ CH}} - )_{x/2} + 2{\text{H}}_{\text{2}} {\text{O}} \to ( - \mathop {\text{C}}\limits_{\mathop \parallel \limits_{\text{O}} } \cdot \cdot \cdot \cdot \cdot \cdot \cdot \cdot \mathop {\text{C}}\limits_{\mathop \parallel \limits_{\text{O}} } - )_{x/2} + 6{\text{H}}^{\text{ + }} + 5e^ - $$ As this process occurs to some extent even in the potential region of Process 1, a continuous degradation of the host lattice occurs upon cycling.     

Studies of space-averaged mass transport in the FM01-LC laboratory electrolyser

Measurements of the mass transport limited current for the reduction of ferricyanide in 1M m potassium hydroxide and of copper(II) in 1.5 m sulphuric acid as a function of electrolyte flow rate are used to characterize the space-averaged mass transport properties of the FM01 laboratory electrolyser, with and without six types of polymer mesh turbulence promoters. In the absence of a promoter, the results followed the equation For the cell with the preferred turbulence promoter, the corresponding equation is Pressure drop data are also reported and it is confirmed that the presence of a turbulence promoter need not lead to a significant increase in the pressure drop over the reactor.     

[CuL(H2O)2]{[CuL][Fe(CN)6]}2·2H2O (L=3,10-Bis(2-hydroxyethyl)-1,3,5,8,10,12-hexaazacyclotetradecane): A Novel Three-Dimensional Coordination Polymer via H-Bonded Linkages of One-Dimensional Zigzag Chain

A complex with the formula [CuL(H₂O)₂]{[CuL][Fe(CN)₆]}₂·2H₂O, where L=3,10-bis(2-hydroxyethyl)-1,3,5,8,10,12-hexaazacyclotetradecane, has been synthesized and crystallographically characterized. The structure is composed of a one-dimensional zigzag chain of units, and [CuL(H₂O)₂]²⁺ units. The one-dimensional zigzag chain extents through linkages. The adjacent two polymer chains are linked by the hydrogen bonding between [CuL(H₂O)₂]²⁺ and [Fe(CN)₆]^3–, forming a 3D supramolecular structure with inner hydrophilic channels. Magnetic susceptibility measurements show no exchange interaction between the Cu(II) and Fe(III) ions due to the longer (axial) bond length.     

Hydrogen half-cells in molten salts. A potentiometric investigation of the systems (Pt or Au) H2O/H2, OH− in fused alkali nitrates

The potentiometric behaviour of the hydrogen electrodes (Pt or Au) H₂O-H₂, OH_–has been investigated in molten (Na_0·5, K_0·5)NO₃ at 503 K. In both cases the potential of the indifferent electrode could be expressed by the general equation [H₂O]/[H₂] [OH^–] which is different from the one expected on the basis of a Nernstian behaviour of the theoretical overall system 2H₂O+2e=H₂+2OH^–.The experimental findings are discussed in terms of mechanistic models involving the actual electrode surface and the standard potential for the theoretical (reversible) hydrogen electrode is calculated: =–·0V(versus Ag/Ag⁺ 0·07 M).     

Formation of organized structures in systems of polyelectrolyte-ionic surfactants

Summary The interaction of polyelectrolytes with ionic surfactants is studied by turbidimetry and electron micrography. The turbidity of the mixed solution of PVS (poly(vinyl sulfate)) and CTAB (cetyltrimethylammonium bromide) showed a sharp maximum at the mole ratio of 11, indicating quantitative binding between PVS and CTAB. A multilayer structure was observed on the electron micrograph only at the mole ratio of PVS:CTAB=21 with a spacing of about 25A. At the mole ratio of PVS:CTAB=11, a single strand structure was observed. The system of ionene polymer (3,4) -SDS (sodium lauryl sulfate) forms a multilayer structure at the equivalent ratio of 11 with a spacing of 20A.     

Activity and selectivity of a {\text{Pd/}}\gamma {\text{ - Al}}_{\text{2}} {\text{O}}_{\text{3}} catalytic membrane in the partial hydrogenation reactions of acetylene and 1,3-butadiene

A ${\text{Pd/}}\gamma {\text{ - Al}}_{\text{2}} {\text{O}}_{\text{3}}$ membrane supported on a macroporous $\alpha {\text{ - Al}}_{\text{2}} {\text{O}}_{\text{3}}$ tube was prepared by sol–gel processing and used in the partial hydrogenation of acetylene and 1,3-butadiene. The average pore diameter of the ${\text{Pd/}}\gamma {\text{ - Al}}_{\text{2}} {\text{O}}_{\text{3}}$ membrane was 3.6 nm. The gases were separated by Knudsen diffusion. The activity and selectivity of the ${\text{Pd/}}\gamma {\text{ - Al}}_{\text{2}} {\text{O}}_{\text{3}}$ membrane was compared to that of ${\text{Pd/}}\gamma {\text{ - Al}}_{\text{2}} {\text{O}}_{\text{3}}$ catalysts used in a conventional packed bed reactor. The highest selectivity to the partially hydrogenated products occurred when the reactant was premixed with H₂ and was passed through the membrane wall.     

Measurement and regulation of oxygen content in selected gases using solid electrolyte cells. IV. Accurate preparation of CO2-CO and H2O-H2 mixtures

Mixtures of CO₂-CO, H₂O-H₂ and Ar-H₂O-H₂ of precise composition were prepared using a zirconia pump and analysed with a zirconia gauge. The ratio was varied from 5×10^–2 to 10⁴ and the ratio from 3×10^–4 to 10^–2. A Faraday's Law test proved to be a simple and reliable procedure for checking the conditions of utilization of these gaseous mixtures and for verifying that no significant disproportionation of CO or leakage along the gas circuit altered the prepared composition. From a practical point of view the best methods of preparing mixtures with low oxygen activity are reduction of carbon dioxide in the range 5×10^–11 to 10^–17 atm and oxidation of inert gas-H₂ in the range 10^–19 to 10^–27 atm at 800°C.     

Magnetic cobalt-zinc ferrite/PVAc nanocomposite: synthesis and characterization

Metal oxide nanoparticles are the subject of current interest because of their unusual optical, electronic, and magnetic properties. In this work, cobalt zinc ferrite ( $ {\text{Co}}_{0.3} {\text{Zn}}_{0.7} {\text{Fe}}_{2} {\text{O}}_{4} $ ) nanoparticles have been synthesized successfully through redox chemical reaction in aqueous solution. The synthesized $ {\text{Co}}_{0.3} {\text{Zn}}_{0.7} {\text{Fe}}_{2} {\text{O}}_{4} $ nanoparticles have been used for the preparation of homogenous polyvinyl acetate-based nanocomposite ( $ {\text{Co}}_{0.3} {\text{Zn}}_{0.7} {\text{Fe}}_{2} {\text{O}}_{4} /{\text{PVAc}} $ ) via in situ emulsion polymerization method. Structural, morphological and magnetic properties of the products were determined and characterized in detail by X-ray powder diffractometry (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM). The XRD patterns of the $ {\text{Co}}_{0.3} {\text{Zn}}_{0.7} {\text{Fe}}_{2} {\text{O}}_{4} $ confirmed that the formed nanoparticles are single crystalline. According to TEM micrographs, the synthesized $ {\text{Co}}_{0.3} {\text{Zn}}_{0.7} {\text{Fe}}_{2} {\text{O}}_{4} $ nanoparticles had nano-needle morphology with an average particle size of 20 nm. The calculated coefficient of variation (CV) of nanoparticles diameters obtained by TEM micrographs was 16.77. The $ {\text{Co}}_{0.3} {\text{Zn}}_{0.7} {\text{Fe}}_{2} {\text{O}}_{4} $ nanoparticles were dispersed almost uniformly in the polymer matrix as was proved by SEM technique. The magnetic parameters of the samples, such as saturation magnetization (M _s) and coercivity (H _c) were measured, as well. Magnetization measurements indicated that the saturation magnetization of synthesized $ {\text{Co}}_{0.3} {\text{Zn}}_{0.7} {\text{Fe}}_{2} {\text{O}}_{4} /{\text{PVAc}} $ nanocomposites was markedly less than that of $ {\text{Co}}_{0.3} {\text{Zn}}_{0.7} {\text{Fe}}_{2} {\text{O}}_{4} $ magnetic nanoparticles. However, the nanocompoites exhibited super-paramagnetic behavior at room temperature under an applied magnetic field.     

Polymerization of substituted acetylenes by (mesitylene)M(CO)3 (M=W,Mo)

Summary Phenylacetylene could be polymerized by (mesitylene)W(CO)₃ in CCl₄ to give a polymer with 12,000 in ca. 80% yield. UV irradiation was unnecessary unlike the W(CO)₆–CCl₄-h catalyst. The present polymerization did not proceed in toluene. The (mesitylene)W(CO)₃ catalyst afforded high molecular weight polymers from phenylacetylenes bearing bulky substituents (e.g., Me₃Si and CF₃) at the ortho position. The Mo counterpart, (mesitylene)Mo(CO)₃, catalyzed the polymerization of 1-chloro-2-phenylacetylene and 1-chloro-1-octyne to provide high molecular weight polymers . Catalytic amounts of Lewis acids accelerated the polymerization of phenylacetylene by (mesitylene)W(CO)₃, but decreased the polymer molecular weight; this polymerization proceeded not only in CCl₄ but also in toluene.     

Synthesis and characterization of polyacrylonitrile grafted with poly(2,6-dimethyl-1,4-phenylene oxide)

Summary Free radical copolymerization of acrylonitrile (AN, M₁) with poly(2,6-dimethyl-1,4-phenylene oxide)--vinylbenzyl ether (PPO-VBE, M₂, _n + 4200g/mol, _w/ _n + 1.04) was performed at 60°C in either a mixture of N,N-dimethylformamide/toluene or tetrahydrofuran, using 2,2-azoisobutyronitrile (AIBN) as initiator. The characterization of the resulting polyacrylonitrile grafted with poly(2,6-dimethyl-1,4-phenylene oxide) (PAN-g-PPO) was performed by 200 MHz ¹H-NMR spectroscopy and solubility.     

Determination of equilibrium silver sulphate concentration in the system Cu-H2SO4-CuSO4-H2O-Ag2SO4-Ag as a function of composition

The value of the ratio \(\gamma _{{\text{Cu}}^{{\text{2 + }}} } /\gamma _{{\text{Ag}}^{\text{ + }} }^2 \) ( \(\gamma _{{\text{Cu}}^{{\text{2 + }}} } ,\gamma _{{\text{Ag}}^{\text{ + }} } \) -are the mean activity coefficients of copper and silver ions, respectively) was calculated from the measured emf of the cell $${\text{Cu(Hg)|H}}_{\text{2}} {\text{SO}}_{\text{4}} {\text{ (}}c_{\text{x}} {\text{)}} - {\text{CuSO}}_{\text{4}} {\text{ (}}c_{\text{y}} {\text{)|Hg}}_{\text{2}} {\text{SO}}_{\text{4}} {\text{, Hg}}$$ and the solubility of Ag₂SO₄ in H₂SO₄ (c _x) and CuSO₄ (c _y) solutions. The concentration of H₂SO₄ in the solution was varied from 0.5 to 2.1 mol dm^?3 that of CuSO₄ from 0.4 mol dm^?3 to saturation. The results were presented as a function: $$\frac{{\gamma _{{\text{Cu}}^{{\text{2 + }}} } }}{{\gamma _{{\text{Ag}}^{\text{ + }} }^2 }} = a_0 + a_1 c_{\text{x}} + a_2 c_{\text{y}} + a_3 c_{\text{x}}^{\text{2}} + a_4 c_{\text{x}} c_{\text{y}} + a_5 c_{\text{y}}^2 .$$ This function allows the estimation of the equilibrium silver ion concentration \(c_{{\text{Ag}}^{\text{ + }} }^{{\text{eq}}} \) in solutions containing both H₂SO₄ and CuSO₄ in the presence of metallic copper. The function is also very useful for the estimation of the \(c_{{\text{Ag}}^{\text{ + }} }^{{\text{eq}}} \) near a working copper electrode.     

Electrochemical behaviour of a new triiron-substituted polyoxomolybdate

A new complex of the Keggin trilacunary polyoxomolybdate (PMo₉) with Fe³⁺ ions, having the formula (PFe₃Mo₉), has been synthesized and characterized by chemical analysis, FT-IR, Raman, UV-VIS-NIR and EPR spectroscopy, as well as by magnetic susceptibility measurements. Cyclic voltammetry performed at different scan rates, pH and supporting electrolyte composition, was used to investigate the electrochemical behaviour of the PFe₃Mo₉ complex in acidic medium and its electrocatalytic effect on H₂O₂ reduction. The voltammetric waves were assigned, and the enhanced electrocatalytic efficiency of PFe₃Mo₉ relative to PMo₉ was attributed to the presence of Fe atoms.     

Kinetics of electroless copper deposition using cobalt(II)-ethylenediamine complex compounds as reducing agents

Electroless copper deposition using Co(II)-ethylenediamine (En) complexes as reducing agents was investigated in 0.4–1.2 M En solutions at 50 and 70 °C. There is a complicated dependence of the process rate on pH, En concentration and temperature. A copper deposition rate up to 6 m h^–1 (50–70 °C) in relatively stable solutions (pH 6) can be achieved. The stoichiometry of the Cu(II) reduction at pH 6–7 corresponds to the reaction:

Reaction in the silver zinc cell

An adiabatic calorimeter was used to measure the thermodynamics of the silver zinc cell. The charge and discharge reactions were shown to take place in two stages involving the production of argentous oxide and argentic oxide respectively. No thermal evidence was found to suggest the existence of a higher oxide of silver. The cell reactions were (1) $$2{\text{Ag + ZnO}} \leftrightharpoons {\text{Ag}}_{\text{2}} {\text{O + Zn, }}\Delta {\text{H = 158}} \cdot {\text{7 kJF}}^{ - {\text{1}}}$$ (2) $${\text{Ag}}_{\text{2}} {\text{O + ZnO}} \leftrightharpoons {\text{Ag}}_{\text{2}} {\text{O}}_{\text{2}} {\text{ + Zn, }}\Delta {\text{H = 176}} \cdot 1{\text{ kJF}}^{ - {\text{1}}}$$ If the cell was left on open circuit for a long period, or the positive electrodes heated, reaction (2) was suppressed and the discharge took place via reaction (1), without any reduction in capacity.     

The state of Rh during the partial oxidation of methane into synthesis gas

The partial oxidation of methane to synthesis gas over an - and a -supported Rh catalyst has been studied at atmospheric pressure using in situ DRIFTS between 823 and 973 K. A surface intermediate species with IR band at 2000 cm^-1, correlating with the CO formation, was observed during the partial oxidation. DRIFT spectra of adsorbed CO at 323 K were used to study the state of Rh during the partial oxidation. The state of Rh at 973 K is proposed to be a matrix of metallic rhodium with clusters of partially reduced oxide phase with isolated Rh⁺ atoms dispersed on the support. Rh oxide with Rh⁺ cations is the state of Rh during partial oxidation of methane at 823 K. This revised version was published online in July 2006 with corrections to the Cover Date.     

Solid state ionics—the electrochemical analog memory cell with solid electrolyte

A new type analog memory cell with variable output voltage has been proposed and its performance examined. The cell construction is $$\begin{gathered} {\text{Ag|RbAg}}_{\text{4}} {\text{I}}_{\text{5}} {\text{|(Ag}}_{\text{2}} {\text{Se)}}_{{\text{0}} \cdot {\text{925}}} {\text{(Ag}}_{\text{3}} {\text{PO}}_{\text{4}} {\text{)}}_{{\text{0}} \cdot {\text{075}}} {\text{|RbAg}}_{\text{4}} {\text{I}}_{\text{5}} {\text{|Ag}} \hfill \\ {\text{ }} \uparrow \hfill \\ {\text{ Pt}} \hfill \\ \end{gathered} $$ in which (Ag₂Se)_0.925(Ag₃PO₄)_0.075 is a mixed conductor exhibiting high ionic and electronic conductivity at room temperature. The potential difference between the silver electrode and the platinum electrode depends on the silver activity in the mixed conductor, and it is changed by passing the current between one silver electrode and the platinum electrode. The output voltage of the cell is changed in the range of 150 to 0 mV. At open circuit, the memorized cell voltage decreased by only 1% over several hours.     

Electrochemical redox reactions of chromium and iron ions in molten NaCl–2CsCl eutectic for pyro-reprocessing of nuclear fuels

Basic electrochemical and spectroscopic properties of Cr³⁺, Cr²⁺, Fe³⁺, and Fe²⁺ were studied to analyze the cyclic redox reactions of Cr and Fe, which may decrease the current efficiency of the electro-winning method using NaCl–2CsCl melts. The formal redox potentials of the and couples, and , in NaCl–2CsCl melts at 923 K were spectroelectrochemically determined to be −0.648 ± 0.005 V and , respectively. These values were determined by measuring electromotive force and UV–VIS absorption spectra at varying concentration ratios of trivalent and divalent ions. Cyclic voltammetry was also carried out to examine the characteristics of the voltammograms for the and couples in NaCl–2CsCl melts. The determined by the spectroelectrochemical method was close to that determined by cyclic voltammetry . The effect of temperature on the in NaCl–2CsCl melts was studied by cyclic voltammetry in the range from 823 to 1,023 K . Diffusion coefficients of Cr³⁺ and Cr²⁺, and , were determined between 823 and 1,023 K to be and , respectively. Molar absorptivities of Cr³⁺ and Cr²⁺ in NaCl–2CsCl melts at 923 K were determined to be 77.8 ± 2.4 M⁻¹ cm⁻¹ at 17,670 cm⁻¹ and 48.0 ± 1.4 M⁻¹ cm⁻¹ at 9,170 cm⁻¹, respectively. In addition, the effects of these ions on the cyclic redox reaction of the pyro-reprocessing process were discussed.     

Analysis of the kinetics for the H2 + - \frac{1}{2}O2 ⇌ H2O reaction on a hot Pt surface in the pressure range 0.10–10 Torr

The H₂ + O₂ ⇌ H₂O reaction on platinum at 700 and 1300 K has been studied. A stagnation flow geometry was used with a gas mixture of H₂ and O₂ at pressures between 0.10 and 10 Torr. Comparing SHG results with simulations using different reaction parameters, it was concluded that , and . LIF measurements showed an ambiguity in the choice of main water-producing channel. Both hydrogen addition with low sticking coefficients and hydroxyl disproportionation with high sticking coefficients are plausible. This revised version was published online in July 2006 with corrections to the Cover Date.