Dielectric absorption in mixtures of anisole with some primary alcohols at microwave frequency

Dielectric properties of binary mixtures of anisole with methanol (MeOH), 1-propanol (1-PrOH), 1-butanol (1-BuOH) and 1-heptanol (1-HeOH) over an entire concentration range have been studied at a fixed temperature 40°C. The dielectric constant (ε′) and dielectric loss (ε″) of the binary mixtures of polar liquids have been determined at a microwave frequency of 9.1?GHz. The static dielectric permittivity (ε ₀) of the liquid samples was also determined using a precision LCR meter. Determined values of static dielectric permittivity (ε ₀) and dielectric permittivity (ε*) at 9.1?GHz frequency were used to evaluate relaxation time (τ) and high frequency limit dielectric permittivity (ε _∞). Dielectric parameters were interpreted in terms of molecular interaction between the anisole and alcohol molecules.     

Concentration and temperature dependent interaction studies using dielectric and thermodynamic methods on mixtures of anisole with o-toluidine and m-toluidine

Molecular interactions in mixtures of anisole with o-toluidine and anisole and m-toluidine have been studied at three different temperatures using the dielectric method with measurements of the static permittivity and permittivity at optical frequency. From the measured values, the Kirkwood correlation parameter, Bruggeman parameter, excess permittivity and thermodynamic excess free energy were computed for the mixtures. Positive and negative values of excess permittivity were obtained for both mixtures. The excess free energy for the anisole+o-toluidine mixture is positive at all three temperatures, whereas mixed values (positive and negative) are obtained for the anisole+m-toluidine mixture. Alignment of the dipoles in both mixtures was identified by Kirkwood factors. The investigation shows that the interaction between the components changes systematically with concentration and temperature and the change is minimum.     

Correlation studies on dielectric and thermodynamic parameters in the binary mixtures of N-methyl aniline and alcohols

The dielectric and thermodynamic studies on polar binary mixtures of N- methyl aniline with alcohols — propan-1-ol and propan-2-ol have been carried out, at different temperatures and mole fractions. LF impedance analyzer, Microwave bench and Abbe’s refractometer are used respectively in radio, microwave (X-Band) and high frequency regions to determine the dielectric data. The experimental data is used to correlate the dielectric and thermodynamic parameters — static permittivity, high frequency permittivity, Kirkwood effective correlation factor, corrective Kirkwood correlation factor, excess permittivity, excess Helmholtz free energy, dipole moment, excessive dipole moment, relaxation time, excess inverse relaxation time and the excess thermodynamic parameters. These parameters are used to interpret the molecular interactions between the molecular species of the liquid mixtures.     

Understanding the molecular interaction and relaxation findings in amphiphilics on solution state using TDR

The dielectric behavior of stearic acid in 1,4-dioxane medium at various temperature 303 K–288 K and frequency regime (10 MHz–30 GHz) determined from the complex dielectric permittivity spectra obtained by Time Domain Reflectometry(TDR). In this frequency range, the dielectric study gives the electrostatic interaction as well as orientational polarizability of complex mixtures of long chain molecules significantly. Dielectric parameters were calculated from the complex spectra of the binary mixture by non linear least square fit method. The excess permittivity (ε^E), correlation factors were calculated for the binary system. Thermal parameters(ΔH-enthalpy, ΔS-entropy and ΔG-Gibbs free energy) were calculated and the direction of reaction is determined. The FTIR spectrum of the binary system recorded and the assignments are discussed. The FTIR spectral assignments confirm the molecular interactions.     

Thermophysical properties of binary mixtures of odichlorobenzene and o-chlorophenol with diethyl ether, tetrahydrofuran, cyclohexane and anisole

Measurement of density and viscosity has been used for evaluating derived parameters for binary system of o-dichlorobenzene and o-chlorophenol with diethyl ether, tetrahydrofuran, cyclohexane and anisole at the different temperatures and at atmospheric pressure. From these, excess parameters have been calculated over entire range of composition. The variation of derived parameters as well as the sign and magnitude of corresponding excess functions has been used to investigate the type and extent of interaction between the component molecules of the binary mixture.     

Temperature studies of dielectric permittivity and mass density pretransitional anomalies in binary mixtures

Results of temperature studies of dielectric permittivity and mass density in binary mixtures are presented. The anomaly of dielectric permittivity as a function of temperature in nitrobenzene-n-alkanes binary mixtures has been studied. Molar dielectric permittivity which takes into account the anomaly of dielectric permittivity and the mass density anomaly has been introduced.     

An effective force field for molecular dynamics simulations of dimethyl sulfone

A rigid five-site united atom model for dimethyl sulfone (DMSO₂) compatible with the GROMOS force field is parametrized and tested. The parameters were optimized with respect to experimental quantities such as liquid density, heat of vaporization, shear viscosity and excess free energy. Good agreement with pure component properties is achieved except for the static dielectric permittivity which is calculated too low. Together with the SPC model for water the new DMSO₂ model was used to study aqueous mixtures at low concentrations and compared to aqueous mixtures of DMSO. It is concluded that interaction parameters for sulfoxide oxygen are not directly transferable to sulfonyl oxygen.     

Phase transition and some physical properties of binary mixtures of two nematogenic compounds showing induced smectic phase

The binary mixtures of nematogenic compounds 4-n-pentyl phenyl 4-n′-hexyloxy benzoate (ME6O.5) and 4-cyanophenyl 4-pentyl benzoate (CPPB) show the presence of induced smectic phase. In this article, we report the phase diagram and the results of refractive index, density, static dielectric permittivity and X-ray diffraction measurements of different binary mixtures of (ME6O.5?+?CPPB) throughout the entire composition range. The density and refractive index values have been analysed to obtain orientational order parameters. The various physical properties of the system have been discussed on the basis of the phase diagram.     

Excess properties of methanol-water binary system at various temperatures

Summary  In this study the viscosities of binary mixtures of methanol and water have been measured in the temperatures ranging from 15 to 45°C. The structural changes occurring as a consequence of molecular interactions in the solutions have been discussed in detail. Nevertheless, it would be of interest to see whether the information obtained from viscosity studies can be corroborated with that obtained from dielectric-constant data. With this aim, the present study on the dielectric behaviour of methanol-water binary solutions has been undertaken. The static dielectric constants, densities and refractive indices have been also measured on the methanol-water mixtures expressed by the mole fraction of methanol (0<x₂<1). Excess dielectric constants, excess volumes, excess viscosities and excess Gibbs energies of activation of the viscous flow and Kirkwood correlation factors have been evaluated using experimental results since these calculations may lead to conclusions concerning the deviation of the system from an ideal-mixture behaviour.     

Dielectric relaxation study of dipropylsulfoxide/water mixtures

The complex dielectric spectra of dipropylsulfoxide (DPSO)/water mixtures in the whole concentration range have been measured as a function of frequency between 100 MHz and 20 GHz at four temperatures between 298.15 K and 328.15 K. The dielectric parameters, static dielectric constant (ε_s), relaxation time (τ) and relaxation strength (Δε) have been obtained by the least squares fit method. The relaxation in these mixtures can be described by two Debye functions, whereas for pure DPSO Cole-Davidson type is valid. The relaxation times of the mixtures show a maximum at about x(DPSO) ≈ 0.3. In the concentration range where a maximum appears, the interaction of DPSO with water is presumably the result of hydrogen bonding between water and the sulfonyl group of the sulfoxide molecule. The concentration and temperature dependent excess dielectric constant and effective Kirkwood correlation factor of the binary mixtures have been determined. The excess permittivity is found to be negative for all concentrations.     

Triboelectric charging and dielectric properties of pharmaceutically relevant mixtures

Binary mixtures of pharmaceutically relevant powders were investigated using dielectric spectroscopy over a frequency range of 10⁻³ to 300 kHz. Two different binary mixtures were studied as a function of concentration; pseudoephedrine hydrochloride in dicalcium phosphate dihydrate and acetaminophen in microcrystalline cellulose, respectively. Dielectric properties obtained from measurements of these systems are reported and found to follow a trend similar to the observed triboelectric behavior after low-shear tumble blending. Powder samples for charge measurement were mixed using a stainless steel blender and dispensed directly into a Faraday pail. For the two binary mixtures studied, low-frequency conductivity calculated from the imaginary part of the complex permittivity (or loss factor) was observed to be sensitive to water content. Furthermore, the unanticipated trends previously reported in the measured specific charge after blending were observed to correspond with the surface charge density calculated from the capacitance of the composite material. The implications of moisture and the physical and chemical properties of these dielectric mixtures are also discussed with supporting results.     

Studies on intermolecular interaction on binary mixtures of methyl orange-water system: excess molar functions of ultrasonic parameters at different concentrations and at different temperatures

Density (ρ), viscosity (η) and ultrasonic velocity (u) of binary mixtures of methyl orange and water were measured at different concentrations and at different temperatures; several useful parameters such as excess volume, excess velocity, and excess adiabatic compressibility have been calculated. These parameters are used to explain the nature of intermolecular interactions taking place in the binary mixture. The above study is helpful in understanding the dye/solvent interaction at different concentration and temperatures.     

RETRACTED ARTICLE: Density,viscosity and speed of sound of benzaldehyde with benzene at 303.15, 308.15, and 313.15 K

The values of density, viscosity and speed of sound for the binary liquid mixture of Benzaldehyde with Benzene were measured over the entire range of composition at 303.15, 308.15, and 313.15 K. These values are used to calculate the excess molar volume (V ^E), deviation in viscosity (Δη), deviation in speed of sound (ΔU), deviation in isentropic compressibility (Δβ _s ), excess internal pressure (Δπ), excess intermolecular free length (ΔL _f ), excess free volume (V _E ^f ) and excess acoustic impedance (ΔZ). McAllister’s three-body interaction model is used for correlating Kinematic Viscosity of binary mixtures. The excess values were correlated using the Redlich–Kister polynomial equation to obtain their coefficients and standard deviations. The thermophysical properties (density, viscosity, and speed of sound) under the study were fit to the Jouyban–Acree model.     

On the Viscoelastic and Dielectric Behavior of Some Organic Compounds and Their Binary Mixtures

The dependence of dielectric relaxation time on the viscosity of the medium is being extensively used to draw certain quantitative conclusions regarding molecular motion and inter-molecular forces in liquids, liquid mixtures, dilute solutions, and multi-component polar solutes in dilute solution. In the absence of proper empirical or theoretical equations for the variation of dielectric relaxation time with viscosity, only the experimental investigations on different systems can give an insight. In the present study, the results of dielectric measurements carried out on pure samples of bromohexane, bromooctane and bromodecane in dilute solutions in different mixed solvents (benzene + paraffin) and on binary mixtures (1 : 1) of (bromohexane + bromodecane); (bromodecane + propyl alcohol) and (propyl alcohol + methyl alcohol) are reported. For comparison, the results of bromodecane + propyl alcohol and propyl alcohol + methyl alcohol are chosen as they form examples of mixture of non-associative + associative and associative + associative liquids, respectively. Different parameters determined using these dielectric measurements are also presented using different models. These studies indicate that the dielectric behavior at microwave frequencies favor the concept of dynamic viscosity and a single viscoelastic relaxation time for the systems under study.     

Dielectric behaviour and hydrogen bond molecular interaction study of formamide-dipolar solvents binary mixtures

The dielectric constant of binary mixtures of formamide with some common dipolar aprotic and protic solvents has been investigated at sixteen molar concentrations over the entire mixing range at 30 °C. The solvents used for binary mixtures with formamide are water, dimethylsulphoxide, N,N-dimethylformamide, acetone, 1,4-dioxane, mono-, di- and trihydric alcohols, and homologous series of 2-alkoxyethanol, 2-(2-alkoxyethoxy)ethanol, and ethylene glycol oligomers. The concentration dependent plots of excess dielectric constant and Kirkwood correlation factor were used to explore the complexes formed between unlike molecules, the molar ratio of a stable adduct, dipolar ordering, hydrogen-bond molecular connectivities, and their strength in the binary mixtures. Results confirmed that the complexation strength of dipolar aprotic solvents with formamide strongly depends on the value of solvent dielectric constant. The dependence of the hydrogen-bond complexation on number of hydroxyl groups and molecular size of the homologous series of the solvents is recognized from the comparative excess dielectric constant values of the mixed solvents.     

Characterization of heterogeneous interaction in binary mixtures of ethylene glycol oligomer with water, ethyl alcohol and dioxane by dielectric analysis

The associating behaviour of the binary mixtures of ethylene glycol oligomer (EGO), i.e. ethylene glycol (EG), diethylene glycol (DEG) and poly(ethylene glycol)s (PEG200, PEG300, PEG400 and PEG600) with water (W), ethyl alcohol (EA) and 1,4-dioxane (DX) over the entire concentration range at 25 °C have been investigated through their accurately measured values of dielectric constant. The static dielectric constant ε_o, high frequency limiting dielectric constant ε_∞, dielectric relaxation strength Δε, excess dielectric parameters ε^E₀ and ε^E_∞, effective Kirkwood correlation factor g^eff and corrective correlation factor g_f of EGO–W, EGO–EA and EGO–DX mixtures were determined to obtain qualitative and quantitative information about the complex formation through H-bond in these systems. Most of the evaluated dielectric parameters of EG and DEG in different ‘cosolvents’ have different characteristics as compared to the PEG–cosolvent mixture. The observed linear and non-linear behaviour of Δε against EGO monomer unit mole fraction X confirms the variation in the homogeneous structures in their binary mixtures with concentration variation. Appearance of the maximum in ε^E₀ against X plots indicates that a complex stable adduct is formed in the EGO–W mixtures at stoichiometric ratio 1:1.7 for lower oligomers but this ratio seems to be 1.7:1 for higher EGO molecules, which confirms that the EGO size and chain flexibility affects the complex formation between EGO and W. In case of EG–EA mixture 1:1 stoichiometric ratio form stable adduct whereas for higher EGO–EA, it is 3:1, at EGO monomer unit level. The complex formation behaviour of DEG–EA has entirely different characteristics when compared to the other studied EGO–EA mixtures. Although, 1,4-dioxane has weak polar behaviour dielectric properties of EG–DX and DEG–DX confirm the formation of stable adducts at the stoichiometric ratio 2:1 of EGO monomer unit mole fraction to the DX. For the higher EGO–DX mixtures, stable adduct forms at the stoichiometric ratio 9:1. Except DEG–EA mixtures, the EGO–W and EGO–EA form the complex with reduction in the effective number of dipoles. In EG–DX mixtures, the heterogeneous species form with a large reduction in the effective number of dipoles, which changes as the effective number of dipoles increases with the increase in monomer repeat units of EGO. Further the net electronic polarization in these binary mixtures increases due to heterogeneous interaction over the entire mixing concentration range.     

Dielectric studies of alkyl acrylates with primary alcohols using time domain reflectometry

Binary polar–polar liquid mixtures of alkyl acrylates (methyl acrylate, ethyl acrylate and butyl acrylate) with primary alcohols (propan-1-ol, butan-1-ol and hexan-1-ol) were subjected to dielectric studies at 303?K for different concentrations using time domain reflectometry (TDR) over the frequency range from 10?MHz to 10?GHz. Static permittivity (ε₀) dielectric constant at high frequency (ε_∞) and relaxation time (τ) were found through dielectric measurements for different concentrations of each system. The Bruggeman dielectric factor, Kirkwood correlation factor and the excess inverse relaxation time were determined and discussed to yield information on the molecular interactions of the systems. Deviations from the linearity of various models suggest molecular association through hydrogen bonding between the ?OH group of alcohols and C=O group of esters. The results also show a dependence of dielectric parameters on the alkyl chain length of both the alcohols and esters.     

Dielectric studies of some binary liquid mixtures using microwave cavity techniques

The excess parameter studies in the microwave frequency region (X-band) on complex dielectric permittivity for the binary mixtures are reported. The methods employed are fixed cavity perturbation technique and adjustable plunger cavity technique. Also Gopalakrishna method is used to calculate the relaxation time of the polar solute in a non-polar solvent. The samples under study are acetonitrile, chlorobenzene, dimethyl formamide, carbon tetrachloride and benzene.     

Dielectric relaxation and hydrogen bonding studies of 1,3-propanediol–dioxane mixtures using time domain reflectometry technique

The complex permittivity, static dielectric constant and relaxation time for 1,3-propanediol, 1,4-dioxane and their mixtures have been studied using time domain reflectometry (TDR). The excess permittivity, excess inverse relaxation time and Kirkwood correlation factor have also been determined at various concentrations of dioxane. Hydrogen bonded theory was applied to compute the correlation terms for the mixtures. The Bruggeman model for the nonlinear case has been fitted to the dielectric data for mixtures.