Search results for "solution"
showing 10 items of 5638 documents
The role of potassium and hydrogen ions in the Prussian Blue ⇆ Everitt's Salt process
1998
Cyclic voltammetry experiments have proved very useful in the knowledge and understanding of the role of the potassium and hydrogen ions during the Prussian Blue ⇄ Everitt's Salt process. While potassium ions act as a stoichiometric reactant, the hydrogen ions play a very important role in the kinetics of the electron-hopping process. The entropy change for the reaction PB ⇄ ES has proved to be dependent on the degree of crystallinity of the film, indicating that this entropy change is related to the fixation of inner counterions on the crystal structure of the films.
The correlation between electrochemical impedance spectra and voltammograms of PB films in aqueous NH4Cl and CsCl
1998
Abstract Voltammetric curves of reduction of Prussian Blue Films to the Everitt’s Salt form and oxidation to the Prussian Yellow form show important differences depending on the supporting electrolyte countercation. The rate of the overall electron-hopping depends on the countercation. Apparent diffusion coefficients are evaluated from impedance spectra at different stabilization potentials. The dependence of the apparent diffusion coefficients on the stabilization potential can help understand the dependence of the voltammograms shape on the countercation nature.
The role of inner counterions within PB films during electrochemical processes
1999
Abstract The shape of voltammograms of Prussian Blue films (ferric ferrocyanide, PB) deposited on ITO (indium–tin oxide) electrodes in aqueous KCl, CsCl and NH 4 Cl solutions has been studied. These results proved a double role of countercations during these electrochemical processes. Countercations can either be only retained within the zeolitic pores of the PB structure forming part of their inner solution, or can also form part of the crystalline structure of PB films by replacing some iron sites. The different electrochemical behaviour of PB films in the three studied solutions (KCl, CsCl and NH 4 Cl) is analysed from this point of view.
Usefulness of F(dm/dQ) Function for Elucidating the Ions Role in PB Films
2007
The conversion process of "insoluble" prussian blue (PB) films into the "soluble" structure has been followed by the simultaneous measurement of current and mass changes during voltammetric experiments and focusing on the possibilities of the use of the instantaneous mass/electrical charge ratio at each potential. A similar procedure was used for the analysis of the mechanism of reduction of PB films to the Everitt's salt form and to follow the partial dissolution of iron species during the oxidation to the prussian yellow form. The possibility of covering PB films by Nafion membranes, which make difficult the transport of anions through it, allows us to discern the role of anions in the so…
Usefulness of the Instantaneous Mass-charge Ratio for Elucidating the Ions Role in the Stabilization and Dissolution Processes in Prussian Blue Films
2007
The conversion process of 'insoluble' Prussian Blue films into the 'soluble' structure has been followed by the simultaneous measurement of current and mass changes during voltammetric experiments and focusing on the possibilities of the use of the instantaneous mass/electrical charge ratio at each potential. A similar procedure was used for the analysis of the mechanism of reduction of Prussian Blue films to the Everitt's Salt form and to follow the partial dissolution of iron species during the oxidation to the Pussian Yellow form. The possibility of covering Prussian Blue films by Nafion membranes which make difficult the transport of anions through it allows to discern the role of anion…
Osmotic pressure of catenanes in solution
1989
We propose a nonuniversal scaling for the osmotic pressure in the case of concatenating ring polymers. The size exponent depends on the molecular weight of the catenans. The effect is more significant the shorter and the stiffer the molecules are.
Structure of Polymers
2014
The structure and thermodynamics of polymers are discussed both with an adapted version of Flory’s regular solution theory and the concept of scaling and random walks. The salient properties of polymers like segregation and elasticity are discussed in terms of these concept. The Flory-Stockmayer theory of gelation is introduced and related to the percolation concept.
Polymer-Polymer Interaction: Consistent Modeling in Terms of Chain Connectivity and Conformational Response
2006
An approach developed for the modeling of polymer solutions is extended to polymer blends. It accounts explicitly for the fact that the segments of a given macromolecule cannot spread out over the entire volume of the system (chain connectivity) and that the space a polymer molecule occupies may change after contact formation between the components of a mixture (conformational response ζ). The validity of the equation obtained for the Flory-Huggins interaction parameter between polymers is tested by means of critical data published for the system PVME/PS. The measured phase diagrams can be modeled equally well by two limiting assumptions concerning the temperature dependence of the conforma…
On the thermodynamic treatment of poly(vinylidene fluoride)/polystyrene blend under liquid—liquid phase separation conditions
1995
Abstract This paper deals with experimental and theoretical investigations on the compatibility of binary of polymer blends in solution. The experimental phase boundary of a crystalline polymer such as poly(vinylidene fluoride) with polystyrene (an amorphous polymer) in dimethylformamide as solvent has been determined by size-exclusion chromatography at 25°C. The composition of the coexisting phases has been used to calculate interaction parameters by means of the Flory—Huggins-type function for the free energy of mixing, including composition dependence of the polymer-polymer interaction parameter and a first correction term denoted as ternary interaction parameter. The calculation of thes…
Biomolecular-solvent stereodynamic coupling probed by deuteration.
1983
Thermodynamic interpretation of experiments with isotopically perturbed solvent supports the view that solvent stereodynamics is directly relevant to thermodynamic stability of biomolecules. According with the current understanding of the structure of the aqueous solvent, in any stereodynamic configuration of the latter, connectivity pathways are identifiable for their topologic and order properties. Perturbing the solvent by isotopic substitution or, e.g., by addition of co-solvents, can therefore be viewed as reinforcing or otherwise perturbing these topologic structures. This microscopic model readily visualizes thermodynamic interpretation. In conclusion, the topologic stereodynamic str…