Range Of Dielectric Constants Research Articles

Effect of solvent on 13C NMR chemical shifts of tetrad methylene carbons of poly(vinyl chloride)

AbstractThe 13C NMR chemical shifts of tetrad CH2 carbons of poly(vinyl chloride) are observed in solvents covering a wide range of relative dielectric constants and show extreme sensitivity to the solvent. The chemical shifts are interpreted theoretically by means of the solvaton‐CNDO/2 MO theory.

Microwave properties of drilling fluids

The application of electromagnetic (EM) techniques to well logging is initiated in an environment dominated by the properties of the drilling fluids. An impulse technique using nanosecond pulses is applied to a coaxial waveguide containing drilling fluids to measure the velocity (dielectric constant ε) and absorption (attenuation coefficient α) of EM impulses. It is the large difference in dielectric constants of water and oil which makes EM propagation techniques attractive for logging. Dielectric properties of some nondispersed drilling fluids (bentonite and attapulgite clays) are found to be largely dependent upon the volume of water present. Both bentonite and attapulgite clays exhibit the same range of dielectric constants (ε = 81 → 75) when the weight percent of clay is increased to 10 percent. In contrast, the microwave attenuations of these two clays are quite different, with that of the bentonite increasing at about 4 times the rate of the attapulgite suspensions. Microwave attenuation measured for a variety of commercial drilling fluids varies over a wide range, with the lignosulfonates the largest (91 dB/m) and oil inverts the smallest (3 dB/m). The oil inverts also have a small dielectric constant (ε = 3 → 6). Temperature dependence of the attenuation for these same drilling fluids is determined in the range from 23 °C to 45 °C to indicate their behavior under in situ conditions.

Effect of a Polar Solvent on the 1JCH Spin-coupling Constants in Chlorine-substituted Ethanes

Abstract The directly-bonded 13C–H spin-coupling constants (1JCH) for two chlorine-substituted ethanes, CHCl2CHCl2 and CHCl2CH2Cl, have been measured in various solvents with a wide range of dielectric constants and/or as a function of the temperature. Also, these two effects were estimated by the finite perturbation theory based on the CNDO/2 approximation with the solvaton theory. Both experimentally and theoretically, the dielectric constant of a solvent affects the 1JCH more than the temperature. It is shown that the solvent effect on the 1JCH spin couplings in CHCl2CHCl2 and CHCl2CH2Cl arises mainly from electronic changes in the solute molecules caused by intermolecular solute-solvent interaction, more than from the change in the population of the rotational isomers.

Infrared study of surface phonon modes in α-Fe2O3microcrystals

Infrared transmission spectra of alpha -Fe2O3 microcrystals much smaller than the wavelength of incident light were measured over a wide range of dielectric constant of the surrounding medium. Features specific to the surface mode absorption were found. Detailed analysis of the observed spectra was made on the basis of the generalised theory of the average dielectric function. It is shown that the observed spectra can be well explained by taking into account the optical anisotropy, the particle shape and the broadening mechanisms.

Kinetics and mechanism of the cationic polymerization of tetrahydrofuran in solution. THF–CH2Cl2 and THF–CH2Cl2/CH3NO2 systems

AbstractCationic polymerization of tetrahydrofuran (THF) in CH2Cl2 solvent and in mixed CH2Cl2/CH3NO2 solvent was initiated with 1,3‐dioxolan‐2‐ylium cations with AsF and SbF anions. Dissociation constants of the polytetrahydrofuranium ion pairs into ions were measured (e.g., KD = 1.5 × 10−5M at 25°C and [THF]0 = 7.0M; CH2Cl2 solvent) and were found to be more than 100 times lower than in CH3NO2 solvent at the same [THF]0 and temperature. The rate constants k and k, measured for degrees of dissociation ranging from 0.03 to 0.35 in CH2Cl2, were the same within an experimental error of measurements (±15% of the value of kp). Dependence of k( = k = k) on the dielectric constant was a monotonous function in three different solvents, namely, CCl4, CH2Cl2, and CH3NO2, which covered a large range of dielectric constants of the medium (from D = 5 to D = 22) and degrees of dissociation of the macroion pairs, α (from 0.03 to more than 0.70). Thus a decrease in the dielectric constant increases the rate constant k in the whole range of studied polarities of the medium. This result confirms an earlier conclusion that the rate constant of propagation does not depend on the state of aggregation of ions and k = k.

Infrared study of surface phonon modes in ZnO, CdS and BeO small crystals

Infrared transmission spectra of ZnO, CdS and BeO particles much smaller than the wavelength of incident light were measured over a wide range of dielectric constants of the surrounding medium, Features specific to the surface-mode absorption were found. Detailed analysis of observed peak frequencies and spectral shapes was made on the basis of the generalized theory of the average dielectric function. It is shown that the observed features of the spectra can be well explained by taking into account both the optical anisotropy and the actual shape of the particles.

Ion solvation in 3-methyl-2-oxazolidone

In continuing previous studies of the solvation behavior of electrolytes in nonaqueous media, a series of tetraalkylammonium tetraphenylborates, cesium and rubidium tetraphenylborates, tetraalkylammonium perchlorates, and tetraphenylarsonium chloride were investigated by proton magnetic resonance spectroscopy in 3-methyl-2-oxazolidone, a solvent with high dielectric constant, high polarity, and wide liquid range. In this study, as in a previous investigation, it was found that salt solutions containing the tetraphenylborate anion were found to shift the proton peaks upfield, indicating an increase in electron density around solvent protons. In this study the same effect has been noted for tetraphenylborate as well as tetraphenylarsonium ion and is attributed to the large diamagnetic anisotropy of the aromatic solute molecules which results in circulation of π electrons induced by the magnetic field. This ring current causes shielding of the solvent protons, and the shielding increases as the concentration of aromatic solute increases, resulting in upfield morement of chemical shift irrespective of whether the aromatic moiety is the cation or anion.

Wide-Range Dynamic Complex Dielectric Constant Measurements Using Microprocessor Control Techniques

This paper describes a measurement system operated by a microprocessor for the dynamic measurement of the complex dielectric constant of sample materials over a wide range of dielectric constants. A Q multiplier technique is used for measuring materials which undergo large dynamic increases in dielectric losses. Such increased losses are often encountered when the temperature, pressure, illumination, etc., of a sample dielectric or semiconductor material are altered; or whenever important changes occur in the molecular structure related to changes in the physical state (e.g., liquid-solid) of the test sample. A complete functional diagram of the microprocessor program is presented. For the purpose of these measurements an AIM 65 microprocessor system is expanded to operate with up to 16 I/O ports and 20K bytes of RAM memory.

An Open Transmission Line UHF CW Phase Technique for Thickness/Dielectric Constant Measurement

A description is given of a system which employs open-balanced transmission line structures and UHF CW phase measurement techniques to determine either the thickness or dielectric constant or moisture content of film or slab-like materials in the thickness range of 1 to 400 mil and the relative dielectric constant range of approximately 2 to 20. Both experimental and analytical results are presented.

Kinetic Studies of Block Polycondensation. I. Aggregation of Various Carboxylic Acids in Solvents of Low Dielectric Constant

Abstract Self-association of benzoic, octanoic, and octadecanoic acids was studied in solvents with a range of dielectric constants between 2.3 and 10. The number-average molecular weights were determined by means of vapor pressure measurements and were carried out at temperatures ranging from 25 to 90° C. It appears that, in these solvents of low dielectric constant, carboxylic acids are present mainly as molecular or ionic aggregates.

Scattering from non-spherical hydrometeors

A new theoretical formulation for scattering from a wide class of non-spherical hydrometeors has been developed recently using Waterman’s extended integral equation technique. The transition or T-matrix formulation is an exact solution to the scattering problem and computer programs have been developed to handle both homogeneous and imbedded bodies (e.g., a dielectric imbedded within another dielectric body). This theory will be briefly reviewed followed by sample computations of backscattering calculations of (a)oblate spheroidal icestones of varying sizes and eccentricities, (b)ice-stones with surface perturbations to model roughness, and (c)rough ice-stones covered with a thin coating of water. The method is realistically applicable for sizes up to D ≈3 λand for a wide range of dielectric constants. Comparisons with measurements of backscattering from a non-concentric dielectric-clad spherical perfect conductor is included.

Scattering from axisymmetric dielectrics or perfect conductors imbedded in an axisymmetric dielectric

Waterman's <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</tex> -matrix formulation of classical electromagnetic scattering from a single, homogeneous scatterer has been extended by Peterson and Ström to include scattering from multilayered scatterers. The <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</tex> -matrix refers to expansions in spherical wave solutions of the vector Helmholtz equation. This theory and the computational method for calculating backscattering cross sections for axisymmetric scatterers are developed. This approach, using the equivalence principle, yields a more concise and systematic development to the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</tex> -matrix formulation than that of Peterson and Ström which relies upon the conceptually similar Poincare-Huygens principle. The method is realistically applicable to scatterers of sizes up to <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ka \sim 2\pi</tex> and for a wide range of dielectric constants. Sample computations are compared with extended Mie theory calculations of scattering by concentric shells of varying size and with measured backscattering cross section obtained from a displaced spherical perfect conductor imbedded in a lossy, spherical dielectric.

Conductance of s-alkylisothiouronium bromides in water-dioxane mixtures

Conductance measurements are reported for S-t-buisBr, S-n-buisBr, S-n-amisBr, and S-n-octisBr in pure water and in water-dioxane mixtures at 25°C in the dielectric constant range 13 < D < 78.5. The data were analyzed by the Fuoss—Onsager equation for associated electrolytes and the characteristic functions are derived. A trial to obtain the transport number of the Br − ion is described. The hydrodynamic radius is calculated for Br − ion and for each of the four cations. Finally the association constant K A is analyzed on the basis of the solvent separated-ion pair model.

Short range electrostatic interactions in dielectric media

The electrostatic theory for a dielectric sphere with arbitrary charge distribution within it is presented. The sphere is located in a dielectric medium which either contains another similar sphere or is separated from another dielectric medium by a planar interface. It is shown that the case of two dielectric spheres is simply related to that of a sphere near a planar interface. The cases of a point charge or a point dipole at the center of the sphere are analyzed in detail. For the point charge case, the numerical results for both the electrostatic potential energy and forces for a wide range of values of the ratio of dielectric constant of sphere to that of medium are given. In addition, approximate analytical expressions are given and constrasted with the exact numerical results. The asymptotic expression occasionally used is shown to provide a good approximation for equal and oppositely charged cavities embedded in a medium of very high dielectric constant. An analytical expression, similar in structure to the exact one for metallic spheres, is derived and shown to provide an excellent approximation over the whole range of dielectric constants and arbitrary charge combinations. Approximate expressions using Padé approximants and simple variational approaches are also given. For the point dipole case, extensive numerical results are presented. It is shown that, for the case of a dielectric cavity, embedded in a medium of high dielectric constant and in contact with another similar cavity with the dipoles oriented along the lines of centers, the potential energy can be expressed in terms of tabulated analytical functions. This also applies for a dielectric cavity in contact with a planar dielectric interface with dipoles oriented perpendicular to the interface.

3-methyl-2-oxazolidone as a solvent for acid-base titrations

3-Methyl-2-oxazolidone has been evaluated as a solvent for the titration of various weak carboxylic acids and phenols. Its high dielectric constant and wide liquid range contribute to its outstanding solvent properties. Tetrabutylammonium hydroxide was the titrant. End-points were determined potentiometrically with a glass-calomel electrode system. FORTRAN computer programs were used to evaluate the results, and relative acid strengths were determined and related to the aqueous acidity. The accuracies obtained are comparable to those for other solvent media. An 800-mV potential span is available in this solvent, which may allow differentiating titrations to be performed. No titrations of acid mixtures were attempted, but it was found possible to distinguish both neutralization steps for salicylic acid and o-phthalic acid.

Liquid ion exchange selectivity of dinonylnaphthalenesulfonic acid (HD) with respect to some lanthanide and actinide ions

The liquid ion exchange selectivity of dinonylnaphthalenesulfonic acid (HD) dissolved in a series of organic diluents covering the dielectric constant range 2·38-34·8 with respect to the cations Ce 3+, Eu 3+, Gd 3+, Tm 3+, Am 3+, Cm 3+, Cf 3+ in perchloric solutions has been studied at 25°C. The extent of aggregation of HD in the different diluents and the equilibrium constants of the exchange reactions have been evaluated. As far as the dependence of the ion exchange selectivity on the diluent nature is concerned, a decrease of the selectivity with the increase of the diluent dielectric constant has been evidenced only in the case of M 33+H- + exchange. The reasons of this behaviour are discussed together with literature data concerning other liquid ion exchange systems.

The helical content of zein, a water insoluble protein, in non-aqueous solvents

The conformation of zein, a seed protein from corn, was determined by optical rotary dispersion measurements in a wide variety of nonaqueous solvents. Over a wide range of dielectric constants, in pure and mixed solvent systems, the helical content was independent of dielectric constant. Determination of the helical content of insulin and ribonuclease in several of these solvents indicated a variation in secondary structure comparable of that of zein. Though virtually insoluble in water, zein not only is a globular protein in nonaqueous solutions, but has conformational properties characteristic of more conventionally behaving globular proteins.

Conductance in isodielectric mixtures. III.i-butyronitrile with chlorobenzene,o-dichlorobenzene,p-dichlorobenzene, 1,2-dichloroethane, andn-pentanol

The conductance of tetrabutylammonium tetraphenylboride, picrate, perchlorate, and nitrate has been measured at 25°C in mixtures ofi-butyronitrile with chlorobenzene,o-dichlorobenzene,p-dicholorobenzene, 1,2-dichloroethane, andn-pentanol covering the range of dielectric constants 10≤D≤20. In these mixtures of polar solvents, both association constants and ionic mobilities depend on ion-solvent interaction energies and on free volume in a manner that is specific for each system. This failure of the primitive model (rigid charged spheres in a continuum) is shown to be the consequence of short-range spatial and energetic interactions between ions and adjacent solvent molecules.

Conductance in isodielectric mixtures. II.i-butyronitrile with benzene, carbon tetrachloride, dioxane, and tetrahydrofuran

The conductance of tetrabutylammonium nitrate, perchlorate, and picrate and of tetraethyl-, tetrapropyl-, and tetrabutylammonium tetraphenylborides has been measured at 25°C ini-butyronitrile and in mixtures of this solvent with benzene, carbon tetrachloride, dioxane, and tetrahydrofuran, covering the range of dielectric constants 10–23.81. The association constant for a given salt is the same in isodielectric mixtures ofi-butyronitrile with the nonpolar liquids; association is greater at a given dielectric constant for the mixtures with tetrahydrofuran. Single-ion mobilities are specific for any ion-solvent combination and therefore cannot be described in terms of the radius of an equivalent sphere and the bulk dielectric constant and viscosity of the solvent.

Dissociation constants and metal chelate stabilities of picolinic acid and pipecolinic acid in 1-propanol-water mixtures: The dependence of the zwitterion form on the dielectric constant of the solvent

The interaction of Ni(II) and Zn(II) with picolinic acid and pipecolinic acid has been studied by potentiometric titrations at 0, 25, and 40°C and ionic strength of 0·02 M in 1-propanol-water mixtures. Dissociation constants of the ligands and formation constants of the chelates containing 1:1 and 1:2 molar ratios of metal ion to ligand in a dielectric constant range of 30–80 are reported. A computer program used in obtaining the dissociation constants is discussed. The predominance of the neutral molecule over the zwitterion form for picolinic acid is discussed.