Water soluble polyaniline and its blend films prepared by aqueous solution casting

Polyaniline (PAn) was doped with phosphonic acid containing hydrophilic tails. The solubility of the doped PAn in water was controlled by changing the length of hydrophilic chain in the dopant. When poly(ethylene glycol) monomethyl ether (PEGME) with molecular weight M-w = 550 was used as the hydrophilic chain of the dopant, the doped PAn was entirely soluble in water. The film cast from aqueous solution showed good electrochemical redox reversibility, Aqueous solution blending of PAn with poly(ethylene glycol) (PEG, M-w = 20 000) and poly(N-vinyl pyrrolidone) (PVP, M-w = 360 000) was achieved. Percolation threshold of the composite film was lower than 3 wt.%. Electrical conductivity of the composite film was in the range of 10(-1)-10(-5) S cm(-1), depending on molecular weight of the acid and the content of PAn in the composite. (C) 1999 Elsevier Science Ltd. All rights reserved.

Separation of phenothiazines using aqueous and nonaqueous capillary electrophoresis

Separations of phenothiazines, promethazine(PZ), dioxypromethazine (OZ), chlorpromazine(CZ), trifluoperazine(TfZ) and thioridazine(TZ) by capillary electrophoresis in water and FA media were carried out and compared. Thus different selectivity and resolution were observed as media varying from water to FA. Migration order was PZ, OZ, CZ and TZ in water but (TZ+PZ), CZ and OZ in FA, when the same buffer, 25 mmol/L Tris and 25 mmol/L citric acid, was used. It also has been observed that pH has great effect on selectivity both in water and FA and a possible explanation was given. Separation efficiency was higher in FA media than in water because of the permission of high voltage applied. For all separations in FA 30 kV was applied, and when 25 mmol/L Tris was used as buffer, current was only 20 mu A and complete separation of TZ, CZ, PZ and OZ was achieved with effencicy higher than 3.5 x 10(5) theoretical plates for all analytes. The high performance of capillary electrophoresis in FA suggests that FA is an excellent media separation.

Main-chain photosensitive polyamic acids using alkaline aqueous solution as developer

In order to develop photosensitive polyimides (PSPIs) imaged in alkaline aqueous solution, a photosensitive diamine and relevant polymer containing conjugated double bonds in the main chain have been synthesized. The photosensitive characteristics and thermal stability of the polymers were investigated. These polymers possess good thermal stability and sensitivity to UV irradiation, and could be used to form a PSPI resist using alkaline aqueous solution as developer. (C) 1999 Society of Chemical Industry.

Phase-separation behavior of the system PES/phenoxy: An application of the Sanchez-Lacombe lattice fluid theory

Cloud-point curves reported for the system polyethersulfone (PES)/phenoxy were calculated by means of the Sanchez-Lacombe (SL) lattice fluid theory. The one adjustable parameter epsilon(12)*/k (quantifying the interaction energy between mers of the different components) can be evaluated by comparison of the theoretical and experimental phase diagrams. The Flory-Huggins (FH) interaction parameters are computed based on the evaluated epsilon(12)*/k and are approximately a linear function of volume fraction and of inverse temperature. The calculated enthalpies of mixing of PES/phenoxy blends for different compositions are consistent with the experimental values obtained previously by Singh and Walsh [1].

Redox reaction of disulfide polyaniline in aqueous solution

The cleavage and formation of the di sulfide bond of 2,5-dimercapto-1,3,4-thiadiazole (DMcT) were examined in an aqueous solution of pH value from 0 to 14 with and without polyaniline (PAn), The redox reaction of DMcT was accelerated by PAn in acidic condition. The cell using this anodic material was set-up and characterized in aqueous electrolyte.

Synchronous fluorescence spectra of hemoglobin: A study of aggregation states in aqueous solutions

The synchronous fluorescence spectra of hemoglobin solutions are reported for the first rime. The main fluorescence peaks observed in the spectra are assigned. The effect of the concentration of hemoglobin solution on the spectra is studied. Characteristic fluorescence peaks due to the dimer and tetramer of hemoglobin molecules are recognized. (C) 1998 Academic Press.

Polymerization of aniline in an aqueous system containing organic solvents

Polyaniline (PAn) with different molecular weight was prepared by adding organic solvents such as acetone, ethanol or THF into the polymerization mixture. Open-circuit potential measurements showed that the polymerization rate was lowered by the addition of the organic solvent Spectral studies showed that PAn intermediate before the oxidant was consumed was pernigraniline and it was reduced to emeraldine base rapidly by aniline in the termination period. A mechanism of chain propagation was proposed. Chain propagation and autoacceleration period were almost independent of addition of pernigraniline, and the autoacceleration of aniline polymerization is due to more rapid initiation rate. (C) 1998 Published by Elsevier Science S.A. All rights reserved.

Catalytic oxidation of cyclohexene to cyclohexanone by a triple system in acidic aqueous acetonitrile medium

The catalytic oxidation of cyclohexene to cyclohexanone using Pd(OAc)(2)/HQ/FePc was investigated in an acidic aqueous solution of acetonitrile. The role of each component of this system in the oxidation of cyclohexene was explored by means of UV-VIS, IR, XPS spectroscopy and. cyclic voltammetry, respectively. Based on the experimental results, the mechanism of the oxidation of cyclohexene catalyzed by Pd(OAc)(2)/HQ/FePc was elucidated.

Application of the Sanchez-Lacombe lattice fluid theory to the system pvme/ps and model calculations

Cloud point curves reported in the literature for five representatives of the system poly(vinyl methyl ether)/polystyrene were evaluated theoretically by means of the Sanchez-Lacombe lattice fluid theory. The measured phase separation behavior can be described within experimental error using only one adjustable parameter (quantifying the interaction between the unlike mers). The Flory-Huggins interaction parameters calculated from this theoretical description depend in good approximation linearly on composition (volume fractions) and on the inverse temperature. An evaluation of these data yields a maximum heat effect which is almost one order of magnitude less (ca. -0.25 J/cm(3)) than obtained via Hess's cycle (dissolution of the components and of the blend) from calorimetric measurements. Model calculations on the basis of the present theory demonstrate that the critical points shift to a different extent upon a certain relative change in the molar mass of the blend components. The sensitivity of the calculated phase diagrams against changes in the scaling parameter decreases in the following order: interaction energies between unlike mers, differences in the scaling temperatures, pressures and densities.

Adsorption of dodecatungstosilicic acid on to activated carbons from aqueous and acidic media

Heteropoly acids (HPAs), such as dodecatungstosilicic acid (SiW12), adsorb strongly on to activated carbons. The surface chemical properties of the activated carbons have a pronounced effect on the adsorption of HPAs. To obtain activated carbons with the desired surface chemical properties, modification with mineral acids has been applied. The adsorption isotherms of SiW12 from aqueous solution and various acidic media on to the various carbons have been studied. On the basis of the results obtained, an adsorption model for HPAs from acidic media is presented.

Electrocatalytic reduction of nitrite using Dawson-type tungstodiphosphate anions in aqueous solutions, adsorbed on a glassy carbon electrode and doped in polypyrrole film

The electrochemical behavior of Dawson-type P2W18O626- adsorbed on a glassy carbon electrode and doped in a polypyrrole film electrode was described. These modified electrodes all display catalytic activity for nitrite reduction, either in acid solutions or in pH > 4.0 solutions.

Adsorption of PMo12 and SiMo12 on activated carbon in aqueous and acidic media

In various acidic media, such as H2SO4, HCl, H3PO4, acetic acid of 3 M in hydrogen ion concentration, and pure acetic acid, the adsorption of heteropolyacids composed of molybdenum with the Keggin structures PMo12 and SiMo12 on different activated carbons is studied. In acidic media, the adsorbed amount of heteropolyacids is much higher than that in water. By considering the relation between adsorbed amount and the acid strength of the media, as far as SiMo12 and PMo12 are concerned, there exist different trends.

Electrochemical behavior of molybdotungsate heteropoly complex with neodymium K10H3[Nd(SiMo7W4O39)(2)]xH(2)O in aqueous solution

The voltammetric behavior of the titled compound (denoted as Nd (SiMo7W4)(2)(13-)) in aqueous solution had been studied. An unusual pH response was discussed. The adsorption of the anion on the dropping mercury electrode and a self-inhibition influence of the adsorbed anions on the redox process of those anions dissolved in solution were found. The electrocatalytic effects of the anion on the bromate reduction were investigated.

Electrochemical behavior of the molybdotungstate heteropoly complex with neodymium, K10H3[Nd(SiMo7W4O39)(2)]center dot xH(2)O in aqueous solution

The electrochemical behavior of the title compound (denoted Nd(SiMo7W4)(2)(13-)) in aqueous solution has been studied using cyclic voltammetry, sampled d.c. voltammetry, differential pulse voltammetry and bulk electrolysis with coulometry, The stable pH range of Nd(SiMo7W4)(2)(13-) is determined with UV-visible spectra. In the potential range between 0.70 and -0.45 V vs. SCE, the anion in pH 3.8 aqueous solution undergoes one-, one-, two- and two-electron steps of four redox processes attributed to electron addition and removal from the molybdate-oxo framework. The adsorption of the anion on the dropping mercury electrode and a self-inhibition influence of the adsorbed anions on the redox process of those anions dissolved in solution are found. The unusual dependence of the formal potentials on pH is explained with the competition of the protonation and ion-pair formation due to the high negative charge of Nd(SiMo7W4)(2)(13-) and its reduced forms. The electrocatalytic effects of the anion on the bromate are investigated.

C-13 NMR study on the aqueous structure of lanthanide citrate complexes

The aqueous complexation of lanthanide complexes of citrate in pH 7.4 solutions has been studied by using lanthanide-induced shift and relaxation times measurement methods. These results indicate that citrate coordinate via 3-hydroxyl and 3-carboxylate groups with lanthanide ions and form 1:2 (Ln/cit) isostructural complexes through lanthanide series. We suggest a new coordination geometry which is different from that described in literature.