D. V. Loginova

Microwave dielectric properties of aqueous solutions of potassium and cesium fluorides

The microwave dielectric properties of aqueous solutions of potassium and cesium fluorides are studied over a wide concentration range at frequencies of 13 to 25 GHz and temperatures of 288, 298, and 308 K. The static dielectric constant ɛs and the time τ and enthalpy of activation ΔHɛ++ of dielectric relaxation for the solutions are calculated. It is demonstrated that, for fluorides, the disruptive effect of ions on the hydrogen bond network of water is weaker than that for the other halogenides.

Effect of dielectric properties and structure of aqueous solutions of diallylammonium salts on their reactivity in radical polymerization

The complex dielectric permittivity in the frequency range 7.5–25.0 GHz and the low-frequency specific conductivity of aqueous solutions of diallylammonium salts (diallylammonium and diallylmethylammonium trifluoroacetates and diallyldimethylammonium chloride) were measured at 293–308 K over a wide concentration range. On the basis of the results, the parameters of dielectric relaxation were calculated. The number of water molecules in the solvation shell of the salts was estimated. The concentration behavior of the initial rate of radical polymerization of diallylammonium salts and the rate constant of bimolecular chain termination was correlated with the specific features of the structure of aqueous monomer solutions. The role of “free” water in the initial salt solutions was revealed, a species whose presence in the system determines the character of concentration behavior of the rate constants for the elementary steps of polymerization, such as propagation, chain transfer to the monomer, and bimolecular chain termination.

Effect of dielectric and structural properties of solutions on the polymerizability of diallylammonium-type monomers

New polymerization systems— N , N -diallyl- N -methylammonium trifluoroacetate (D1TFA) and N , N -diallylammonium trifluoroacetate (D2TFA)—exhibit phenomena that distinguish their behavior during radical polymerization (Scheme 1) from the known cases, in particular, from the quaternary N , N -diallyl- N , N -dimethylammonium chloride (D3C). These phenomena are evidence of a substantial effect of the medium on the basic polymerization characteristics of new cationogenic monomers: the initial polymerization rate V , the average length of the polymer chain P n , and the constant of chain transfer to the monomer C m [1].

Microwave dielectric permittivity and relaxation of aqueous potassium trimethylacetate solutions

The MW dielectric properties of aqueous potassium trimethylacetate (pivalate) solutions have been measured at six frequencies (10–25 GHz) at 288, 298, and 308 K. The static dielectric constants and dielectric relaxation times and activation parameters have been calculated. Trimethylacetate ion leads to the decrease in the mobility of water molecules and strengthening of their hydrogen bonds. These changes of water are similar to those in solutions of other carboxylates with a large number of nonpolar groups. The hydrophobic hydration of the trimethylacetate ion is maximal in this series.

Microwave dielectric properties of potassium hydroxide aqueous solutions

Microwave dielectric properties of potassium hydroxide aqueous solutions were studied at frequencies of 13 to 25 GHz over a wide range of concentrations and temperatures of 288 to 308 K. Experimental electrical conductivity data were used to determine ionic losses at high frequencies. The static dielectric permittivity σs, dielectric relaxation time τ, and thermodynamic activation parameters of dielectric relaxation (ΔHɛ++, ΔGɛ++, and ΔSɛ++) were calculated. These quantities decrease in transfer from water to solutions. Thereby we demonstrate that potassium hydroxide has a disturbing effect on the initial hydrogen-bond network of water.

Microwave dielectric properties of aqueous trifluoroacetic acid solutions

Microwave dielectric properties of aqueous trifluoroacetic acid solutions are determined in the region of maximal permittivity dispersion of water (10–26 GHz) at temperatures of 288, 298, and 308 K. Static dielectric permittivities and dielectric relaxation times and activation parameters are calculated. The molecular-kinetic stabilization of water is observed in the solutions under study at a lowered temperature (288 K). Increases in degree of connectivity and in degree of structuring of the H-bond network of water in aqueous trifluoroacetic acid solutions are inferred from an analysis of temperature-induced changes of the relaxation effects, which are dictated by the hydrophobic hydration of trifluoroacetate ion, in turn associated with the effect of its low-polarity CF3 group.

Dielectric constant and dielectric relaxation in aqueous solutions of K2[PdCl4] and K2[PtCl4]

The MW-dielectric properties of aqueous solutions of K2[PtCl4] (I) and K2[PdCl4] (II) were studied at 298 and 313 K in the frequency range (12–25 GHz) corresponding to the maximum dielectric constant dispersion for water and aqueous solutions of these salts. The low-frequency conductivities were measured. The static dielectric constant, the dielectric relaxation time, and the enthalpy of activation of the dielectric relaxation of the solutions were determined. Compared to pure water, in solutions of salts I and II, the orientational mobility of water molecules is increased and the network of H-bonds is violated more strongly than that of most other ions with hydrophilic hydration. It was demonstrated for the first time that dielectric spectroscopy can be used for analyzing complexation processes in systems containing aqua and hydroxo chloride complexes of metals.