Search results for "lectrolyte"
showing 10 items of 747 documents
Room temperature ionic liquids based on cationic porphyrin derivatives and tetrakis(pentafluorophenyl)borate anion
2011
A series of 11 low melting ionic liquids based on meso-substituted A3B -porphyrins and A2B2-porphyrins containing one or two pyridyl substituents have been synthesized in high yields. Three of them are liquids at room temperature. All these porphyrinic salts were characterized by1H NMR,19F NMR, MALDI-TOF mass spectrometry, elemental analysis and UV-visible spectroscopy. The thermal properties and conductivity values of these salt derivatives have been also measured. A specific conductivity value of up to 4 mS.cm-1could be obtained for a compound having the counter-anion B(C6F5)4-.
Investigation of the Electrophoretic Mobility of the Actinides Th, U, Np, Pu, and Am in Different Oxidation States.
2019
The electrophoretic mobilities (μe) of the actinides Th and U-Am in different oxidation states (prepared in 1 M HCl and 1 M HClO4) have been determined by capillary electrophoresis (CE)-inductively coupled plasma mass spectrometry (ICPMS) using 1 M acetic acid as the background electrolyte, which has proven to provide an excellent setup for trace analysis at environmentally relevant concentrations (1 × 10-9 M). The values are independent of the respective acid solution. The μe of the Pu oxidation states +III to +VI have been measured. They agree with both the available literature data and the redox-stable analogues (Eu(III), Th(IV), Np(V), U(VI)) that have also been investigated. The trend …
Amphotropic Ionomers by Attachment of Secondary Amines to a Reactive Ester Polymer
2004
We report on the synthesis of polyacrylamides that were prepared by the reaction of a reactive ester polymer with a mesogen-containing secondary amine and N-methyl-piperazine. As the polymers do not form hydrogen bonds near the amide groups, their mobility is significantly higher than that of poly(N-monoalkylacrylamides). The initially nonionic polymer shows no liquid-crystalline behavior in bulk and in mixture with ethylene glycol. This is due to the low polarity difference between the different side chains. The polarity difference can be increased by protonation or quarter-nization of the tertiary amino groups, and liquid-crystalline behavior is observed. The self-assembly multilayer buil…
Molecular Recognition by Hydrogen Bonding in Polyelectrolyte Multilayers
1997
Functional polyanions were prepared by copolymerization of sulfopropyl acrylate and sulfopropyl methacrylate with monomers bearing triaminopyrimidine or barbituric acid functionalities, respectively. Functionalized polyelectrolyte multilayers were assembled from these copolymers by stepwise alternating adsorption with poly(choline methacrylate). These multilayers are suited for molecular recognition of substrates that are complementary to the functional groups incorporated. Thus, multilayers containing triaminopyrimidine moieties selectively bind barbituric acid, and vice versa, when exposed to solutions of the 1:1 complex of barbituric acid and triaminopyrimidine. The molecular recognition…
Multi-Arm Star Polyglycerol-block-poly(tert-butyl acrylate) and the Respective Multi-Arm Poly(acrylic acid) Stars
2006
Well-defined multi-arm star block copolymers, polyglycerol-block-poly(tert-butyl acrylate) (PG-b-PtBA), with average arm-numbers of 17, 27, 36, 66 and 90 arms, respectively, have been prepared by atom transfer radical polymerization (ATRP) of tBA in acetone, using a core-first strategy. After hydrolysis with excess concentrated HCl in refluxing dioxane, full hydrolysis of the tert-butyl ester groups was achieved, resulting in multi-arm star polyelectrolytes, polyglycerol-block-poly(acrylic acid) (PG-b-PAA). The hyperbranched macroinitiators employed were prepared on the basis of hyperbranched polyglycerols via esterification with 2-bromoisobutyryl bromide. Both CuBr/PMDETA and CuBr/Me 6 TRE…
Effect of the reference solution in the measurement of ion activity coefficients using cells with transference at T=298.15K
2010
Abstract This work reports individual activity coefficients of ions at T = 298.15 K in aqueous solutions obtained from voltage values of the respective half-cell ion-selective-electrode and a single-junction Ag–AgCl reference electrode, filled with different reference solutions at different concentrations. For potassium and chloride ions in KCl aqueous solutions, reference solutions of KCl, NaCl, or CsCl were used. For sodium and chloride ions in aqueous NaCl solutions, reference solutions of CsCl were used. Experimental runs were performed at molalities (1, 2, and 3) m of the reference solution. The concentration of the sample solution was increased, starting from around 1 · 10−3 m, up to …
Physicochemical characterization of passive films on niobium by admittance and electrochemical impedance spectroscopy studies
2005
An analysis of the electronic properties of amorphous semiconductor-electrolyte junction is reported for thin (D ox < 20 nm) passive film grown on Nb in acidic electrolyte. It will be shown that the theory of amorphous semiconductor-electrolyte junction (a-SC/EI) both in the low band-bending and high band-bending regime is able to explain the admittance data of a-Nb 2 O 5 /El interface in a large range (10 Hz-10 kHz) of frequency and electrode potential values. A modelling of experimental EIS data at different potentials and in the frequency range of 0.1 Hz-100 kHz is presented based on the theory of amorphous semiconductor and compared with the results of the fitting of the admittance data…
Buildup of Ultrathin Multilayer Films by a Self-Assembly Process: II. Consecutive Adsorption of Anionic and Cationic Bipolar Amphiphiles and Polyelec…
1991
We have recently reported on the consecutive physisorption of anionic and cationic bipolar amphiphiles onto charged surfaces, adsorbed out of aqueous solutions [1]. Here, we extend our previous concept to multipolar compounds such as polyelectrolytes. In contrast to the bipolar amphiphile system, it is not necessary to separate single charges by a rigid unit, when the polyelectrolyte is adsorbed from sufficiently concentrated solutions. In this case the physisorbed layer does not bind with all ionic groups to the surface and exposes free ionic groups at the new film/solution interface. Therefore a polyelectrolyte layer can replace a layer of bipolar amphiphiles in the consecutive buildup of…
Layer-by-Layer Adsorption: The Solid/Liquid-Interface as a Template for the Controlled Growth of Well-Defined Nanostructures of Polyelectrolytes, Pro…
1994
This report describes the construction of ultrathin films whose structure can be tailored on the molecular scale. The resulting supramolecular film architectures may include functional biological macromolecules such as proteins or polynucleotides. The average distances of two functional layers can be adjusted on the nanometer scale (from less than lnm to several tens of nanometers), with a precision of approximately 0.1 nm. This control is achieved by varying the number and the thickness of the polyelectrolyte interlayers and requires the capability of steering each adsorption step with high accuracy. A crucial factor is the fabrication and manipulation of the film surface at each adsorptio…
Effect of loperamide on jejunal electrolyte and water transport, prostaglandin E 2-induced secretion and intestinal transit time in man
1991
Jejunal perfusion was performed in 12 healthy volunteers to evaluate the dose dependent effects of loperamide on intestinal absorption, stimulated secretion and transit. In 6 volunteers intestinal perfusion of the jejunal segment with isotonic NaCl solution was followed by addition of loperamide in increasing doses (2–8 mg·l−1). The volunteers were pretreated with 1 mg·l−1 prostaglandin E2 (PgE2) in the perfusate before addition of 4 mg·l−1 loperamide. Phenolsulphonphtalein (PSP) boluses (2 ml) were given to measure mean transit time (MTT). Loperamide 2 mg·l−1 converted the minor secretion after perfusion with the standard solution (water −1.45 ml·min−1, Na −0.09 and Cl −0.04 mmol·min−1) to…