Excess Permittivity Research Articles

Dielectric relaxation study of pyridine-n-propyl alcohol mixture using time domain reflectometry technique

ABSTRACT The Time Domain Reflectometry (TDR) technique was used to analyse the complex permittivity spectra of the Pyridine-n-propyl alcohol mixture across the concentration and temperature range of 10–25°C. The Cole-Davidson model was used to match the Pyridine- n-propyl alcohol complex permittivity spectra. The nonlinear least squares fit approach has been used to obtain the Static dielectric constant (ε0), Relaxation time (τ), Effective Kirkwood correlation factor (geff) Excess permittivity ε 0 E , Thermodynamic parameters (activation enthalpy and activation entropy), and Bruggeman factor (fB). Furthermore, the analysis of excess characteristics and the Bruggeman factor points towards the presence of hydrogen bonding between the pyridine and n-propyl alcohol molecules.

H-bonding interaction study for binary mixtures of methyl cellosolve and ethanol: a dielectric, FTIR spectroscopic and volumetric approach

The dielectric measurement of neat ethylene glycol monomethyl ether (EGMME), neat ethanol and their binary mixtures have been carried out using time domain technique in frequency range of 10 MHz to 50 GHz at the temperature range from 10 °C to 25 °C with a difference of 5 °C. The frequency domain technique within the frequency range of 20 Hz to 2 MHz is used to obtain complex dielectric permittivity ε*(ω), electrical modulus M*(ω), complex electrical conductivity σ*(ω) and loss tangent (tan δ) at 25 °C. The dielectric spectra obtained using TDR technique are fitted in Cole-Davidson model to extract the dielectric parameters such as static dielectric permittivity (ε s), relaxation time (τ) and asymmetric distribution parameter (β). These relaxation parameter values are used to predict intermolecular hydrogen bonding between EGMME and ethanol molecules. Furthermore, the inter-molecular interactions through H-bonding between EGMME and ethanol molecules have been confirmed and discussed using Kirkwood correlation factor, excess permittivity, thermodynamic parameter, Bruggeman factor, excess molar volume, excess dielectric permittivity at high frequency and Fourier transform infrared (FTIR) spectra.

Dielectric relaxation and thermodynamic study of aqueous Glycine using time domain reflectometry technique

Using the Time Domain Reflectometry technique in the frequency range of 10 MHz to 50 GHz, the complex permittivity spectra of Glycine (Gly) with water combination have been determined over the complete concentration range of mole fractions and in temperature range of 10–25 °C. The Cole-Davidson model was used to fit the intricate permittivity spectra for Gly and water.The non-linear least square fit method has been used to compute the static dielectric constant (ε0), relaxation time (τ), effective Kirkwood correlation factor (geff), excess permittivity (ε0E), (1/τ)E excess inverse relaxation time (1/τ)E and Bruggeman factor (fB). An automated density and sound velocity meter, the Anton Paar DSA 5000 M and viscosity with Lovis 2000 M/ME, was used to measure the density, sound velocity, and viscosity of aqueous solutions. FT-IR spectra are used to identify the conformation assessments of hydrogen bonding development between complicated mixtures.

Unravelling hydrogen bond network in methanol-propanol mixtures via molecular dynamics simulation and experimental techniques

ABSTRACT Hydrogen-bonded networks in 1-propanol-methanol binary mixture are studied using molecular dynamics simulation along with experimental techniques (FTIR, dielectric spectroscopy and refractive index measurements) for the entire concentration range. The structure of hydrogen-bonded networks is studied through radial distribution function, hydrogen bond statistics and graph theoretical analysis from molecular dynamics. It is observed that the probability of hydrogen bonding is maximum in methanol molecules followed by hydrogen bonding between methanol and 1-propanol molecules and minimum among 1-propanol molecules, as the concentration changes. The graph theory results show the formation of linear chain hydrogen bond networks, with no caged structures, which is validated from the experimental results. Further, the deconvolution of the FTIR OH peak suggests the presence of linear multimers in all concentrations of the binary system. Average degree of the hydrogen-bonded networks from graph theory indicates a complex networks among pure alcohols and dimers between methanol and 1-propanol in their binary mixtures at all concentrations. The negative values of excess permittivity indicate that the components of the mixture interact in a manner such that the net dipole polarisation decreases.

Dielectric, refractometric, and volumetric studies on mixing behavior of two structurally related ketones and glycols systems

The dielectric, refractometric, and volumetric properties were systematically investigated for eight binary systems containing two structurally related ketones (methyl isobutyl ketone and mesityl oxide) and four glycols over the entire composition range at 298.15 and 101 kPa. The selected glycols were (1,3-butylene glycol, pentamethylene glycol, diethylene glycol, and triethylene glycol). The experimental data were analyzed using different approaches in terms of intermolecular interactions between the constituent molecules through excess parameters of different physical quantities. The excess parameters confirm the formation of multimer structure during the mixing process. In addition, the refractive index deviations were calculated in terms of volume fraction. Based on the Iglesias-Reis approach, the influence of the interactions in excess Helmholtz energy and excess permittivity from total interactions follow the same order 1,3BG > DE > PG > TEG for their mixtures with the ketones. All the excess Kirkwood correlation factors (giE) are negative but very small for the mixtures. Thus, the Kirkwood correlation factors for binary mixtures (g12) are not very far from the ideal behavior, and therefore, the dipoles preferentially oriented parallel interrupted for some extent by the mixing process. The Redlich–Kister type polynomial equation was used to fit the experimental excess parameters.

Investigation on interaction of quinoline with primary alcohols: An understanding on dielectric dispersion and relaxation dynamics over a wide frequency regime

The complex dielectric properties of quinoline with methanol and ethanol in solution state were studied in the microwave frequency (10 MHz-30 GHz) at different temperatures (303 K- 288 K) by decreasing 5 K steps using Time Domain Reflectometry (TDR). The complex spectra obtained is used to elucidate the dielectric behaviour of quinoline with solvents. The relaxation time and static dielectric constant determined expresses the relaxing properties of solution. The dielectric permittivity over the entire frequency provides the dielectric dispersion of quinoline complex. The inter and intra molecular interactions are facilitated by the π-electron cloud of aromatic ring and replacement of hydrogen takes place in the nitrogen in the fused ring of quinoline. The correlation factors (g and geff), Bruggeman factor and excess permittivity of the complex mixture envisage the molecular orientation and interaction respectively. The thermal parameters enthalpy, entropy and Gibb’s free energy were determined from the obtained dielectric parameters. The FT-IR spectral assignments indicate the molecular interactions among the constituent of the complex mixture.

Dielectric spectroscopy and molecular dynamic simulation study of binary mixtures of benzaldehyde and methanol at 303.15 K

The complex permittivity spectra in the frequency range of 20 Hz to 2 MHz for benzaldehyde (BZ), methanol (MeOH) and their binary mixtures at 303.15 K temperature are investigated. To understand the molecular behavior and relaxation processes under varied condition of concentrations of BZ in MeOH, various formalisms namely complex impedance and complex ac conductivity derived from complex permittivity spectra have been investigated and linked. Excess static permittivity and Kirkwood correlation factor have been used to comprehend the H-bond dynamics, and are correlated to MD Simulation. The electronic polarizability and molar volume were determined with the help of density and refractive index of the mixtures. The molecular interaction at atomistic level of several binary mixtures is examined using molecular dynamic (MD) simulation. Linkage dynamics of H-bonds, their length, and dc conductivity of the mixture solutions all contribute to a better knowledge of molecular interaction.

Temperature Dependent Dielectric Relaxation Studies of 2-Nitrotoluene-DMSO mixture using Time Domain Relectometry from 10MHz to 50GHz

The dielectric relaxation properties of 2-Nitrotoluene (2-NT) with DMSO for 11 different concentrations has been studied in the frequency range from 10 MHz to 50 GHz using time domain reflectometry (TDR) method. In this frequency range Dielectric relaxation spectra of 2-NT-DMSO mixtures shows Debye type behavior. The temperature dependent static dielectric constant and relaxation time have been determined from 20oC to 5oC. Effective Kirkwood correlation factor is calculated to determine the effect of strong directional forces such as microwaves on heterogeneous molecules under different temperatures. The excess permittivity and excess inverse excess relaxation time is found to be negative for 2-NT-DMSO system with weak molecular interactions. The activation enthalpy have been calculated to find the energy required to rotate the molecules

Structural and molecular dynamics of methyl acetate-xylene solutions using dielectric relaxation spectroscopy

Frequency, temperature and composition dependent complex permittivity spectra (CPS) of Methyl Acetate (MA)-Xylene solutions were measured using Time Domain Reflectometry (TDR) technique from 10 MHz to 50 GHz. The Debye relaxation model has been used to obtain dielectric relaxation parameters of methyl acetate-xylene solution for all concentrations and temperatures. Dielectric constant and relaxation time increases with increase in concentration of MA in Xylene. Objective of this manuscript is to investigate and offer more pertinent data concerning static dielectric parameters, excess permittivity, excess inverse relaxation and Bruggeman factor at higher frequency which has been obtained to understand dielectric behavior of MA-Xylene binary solutions such that calculation of these parameters is an attempt to reveal ideal or non-ideal nature of solutions at different compositions in relation to specific or non-specific intermolecular interactions.

Microwave assisted co-operative dynamics and structural variations in chlorobenzene-acetonitrile solutions

Molecular interactions between CBZ-ACN at 8.845 GHz of microwave frequency region confer structural behavior of molecules such that either monomers or multimers are present in the agreed binary mixtures. Effect of microwave frequency on molecular interactions and hydrogen bonding between C≡N (nitrile) molecule and Cl (chlorine) molecule of CBZ and ACN binary solutions has been studied using X-band microwave technique at 301ºK. Co-operative dynamics and hydrogen bonding between nitrile and chlorine group molecules has been thoroughly explicated thereby obtaining static dielectric constant, excess permittivity, Kirkwood correlation factor using Luzar model and Bruggeman factor.
 Bangladesh J. Sci. Ind. Res. 57(2), 85-90, 2022

Hydrogen Bonding in 1‐Propanol‐Ethanol Binary Mixture: Experimental and Modeling Approaches

AbstractHydrogen bonds between the constituent molecules determine the physical properties of binary liquids. In this work, we explore the nature of hydrogen bonding in ethanol‐propanol system through experimental and computational techniques. The refractive index, dielectric spectroscopy and infrared spectroscopy along with molecular dynamic simulations of 1‐propanol‐ethanol binary system over the entire concentration range are reported here. The excess static permittivity and excess relaxation time shows the evidence of hydrogen bonded multimer structures. The deconvoluted OH peaks from IR spectra indicate the presence of trimers, tetramers and pentamers. The linear decrease in refractive index indicates the absence of caged structures. Molecular Dynamics simulations confirm the presence of the multimers and the absence of caged structures. Radial distribution function shows the binary mixtures exhibit no structural change throughout the concentration range. We also examine the H‐bonding networks present in these systems via graph theoretic analysis.

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 (εE), 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.

Dielectric relaxation study of aqueous glycol ethers with water using time domain reflectometry technique in the frequency range 10 MHz to 50 GHz

The Complex permittivity spectra of glycol ether (GE) compounds such as ethylene glycol mono-methyl ether (EGME), ethylene glycol ethyl ether (EGEE) and ethylene glycol butyl ether (EGBE) with water mixture over entire concentration range and at 25 °C has been determined using Time Domain Reflectometry technique in the frequency range 10 MHz to 50 GHz. The complex permittivity spectra for GE–water were fitted in Cole–Davidson model. The Static dielectric constant (ε0), Relaxation time (τ), effective Kirkwood correlation factor (g eff), excess permittivity () and Bruggeman factor (fB ) have been calculated by non-linear least square fit method. The intermolecular interactions between GE-water binary mixtures suggest the non-linear behavior of dielectric parameters. The contribution of hydrogen bonding interactions among the solute-solvent mixtures is confirmed by Excess properties and Bruggeman factor.

Investigation of dielectric spectrums, relaxation processes, and intermolecular interactions of primary alcohols, carboxylic acids, and their binary mixtures

An easy-to-integrate and easy-to-calibrate circular-coaxial waveguide junction is proposed for the broadband dielectric characterization of liquid from 0.1 GHz to 18 GHz. The dielectric spectrums of four monohydroxy alcohols (methanol, ethanol, 1-propanol, and 1-butanol), four monocarboxylic acids (formic, acetic, propionic, and oleic acids), and their binary mixtures were measured. Their relaxation parameters were retrieved by the suitable Debye relaxation models to determine excess permittivity, excess Gibbs activation energies, Kirkwood correlation factors, and Bruggeman factors of the four acid–ethanol mixtures. These data can be consistently interpreted by different microscopic processes, including the association and dissociation of hydrogen-bound networks under molecular interaction, the parallel or antiparallel orientational rearrangement between heterogeneous dipoles, and the steric hindrance due to the alkyl group. This work not only provides a deeper insight into the fundamental nature of the relaxation processes in polar-polar mixtures but also presents valuable data for the esterification process designs in industrial productions.

Density, speed of sound, refractive index and relative permittivity of methanol, propan-1-ol or pentan-1-ol + benzylamine liquid mixtures. Application of the Kirkwood-Fröhlich model

Densities (ρ), speeds of sound (c), relative permittivities at 1 MHz (εr) and refractive indices at the sodium D-line (nD) at T = (293.15 K to 303.15 K) and p = 0.1 MPa are reported for binary liquid mixtures alkan-1-ol + benzylamine. Methanol, propan-1-ol and pentan-1-ol are the alkan-1-ols studied in this work. The values of the excess molar volume (VmE), excess isentropic compressibility (κSE), excess speed of sound (cE), excess refractive index (nDE), excess relative permittivity (εrE) and its temperature derivative (∂εrE/∂T)p are calculated, and they are adjusted to Redlich-Kister polynomials. The VmE values are negative, indicating a predominance of the solvation between unlike molecules and structural effects. εrE values indicate a positive contribution from the creation of (alkan-1-ol)-benzylamine interactions, and the positive value for the methanol mixture emphasises the importance of solvation. Calculations on excess molar refractions point out to weaker dispersive interactions than in the ideal mixture, which may be explained by the mentioned solvation effects. The Kirkwood-Fröhlich model has been applied to the mixtures, and the Kirkwood correlation factors suggest an important relative weight, especially in the methanol system, of linear-like molecules in the solutions, which is in accordance with the positive contribution of the formed multimers to εrE due to their good effective response to the electric field.

Molecular interaction studies of hydrogen-bonded N-Methyl-2-Pyrrolidone /Ethanol binary mixtures by dielectric relaxation spectroscopy and their temperature dependence

Complex permittivity of the binary mixtures of N-Methyl-2-Pyrrolidone (NMP) with Ethanol (ETH) has been studied in the microwave frequency range at various temperatures. The binary liquid system NMP-ETH is selected to interpret the effect of carbonyl (-CO) group of NMP and hydroxyl group (-OH) of ETH on the volumetric, thermal and dielectric properties. The dipole moment (μ) and relaxation time (τ) is evaluated from Higasi's method and Havriliak-Negami equation. The excess molar volume (VmE), excess permittivity (εE), excess refractive index (nDE), excess inverse relaxation time (1/τ)E are fitted with the Redlich-Kister equation. The results obtained from Polarizable Continuum Model (PCM) and Integral Equation Formalism Polarizable Continuum Model (IEFPCM) solvation theories using DFT methods are correlated with the experimentally determined parameters. The molecular association and chemical stability of the system is interpreted in terms of single-point energy, HOMO-LUMO calculations. The existence of a hydrogen bond within the NMP-ETH system is confirmed from the FT-IR, UV–Vis's spectra.

Molecular interaction studies of isopropyl acetate-xylene mixture using dielectric relaxation approach

Dielectric relaxation parameters of Isopropyl acetate (IPA)-xylene mixtures with different concentrations and temperatures have been measured in the frequency range of 10 MHz to 30 GHz using time domain reflectometry technique. Static dielectric constant, relaxation time, excess permittivity, excess relaxation time, Bruggeman factor, Kirkwood correlation factor and thermodynamic parameters have been determined to understand molecular association between the IPA and xylene molecules. For entire concentrations of IPA-xylene mixture the Kirkwood correlation factor is less than one which shows the antiparallel nature of electric dipole orientation. The experimental values of dielectric constant obtained from time domain reflectometry are in well agreement with theoretical values of dielectric constant obtained by Luzar model. Positive values of enthalpy and entropy indicating that the system is endothermic and less ordered while Gibbs free energy decreases with increase of IPA in xylene.

Dielectric relaxation and co-operative dynamics of propylene glycol – Ethanol mixtures using time domain spectroscopy

The dielectric measurement of propylene glycol (PG) – ethanol (ETH) mixtures over whole composition range have been carried out using time domain technique in the frequency range of 10 MHz to 50 GHz. The measurements were carried out at temperatures 25 °C, 15 °C and 5 °C. Dielectric parameters were evaluated by fitting the complex permittivity data in Cole-Davidson model using non linear least square method. Dielectric relaxations and co-operative dynamics of PG-ETH molecules in pure and their mixtures were discussed using Kirkwood correlation factor (geff), excess permittivity (ε0E), thermodynamic parameter.

Density, speed of sound, refractive index and relative permittivity of methanol, propan-1-ol or pentan-1-ol + aniline liquid mixtures. Application of the Kirkwood-Fröhlich model

Densities (ρ) and speeds of sound (c) at a temperature T = 298.15 K, relative permittivities at 1 MHz (εr) and refractive indices at the sodium D-line (nD) at T = (293.15 K to 303.15 K), all of them at a pressure p = 0.1 MPa, are reported for binary liquid mixtures alkan-1-ol + aniline. The alkan-1-ols considered are methanol, propan-1-ol and pentan-1-ol. Also, the values of the excess molar volume (VmE), excess isentropic compressibility (κSE), excess speed of sound (cE), excess refractive index (nDE), excess relative permittivity (εrE) and its temperature derivative (∂εrE/∂T)p are calculated and fitted to Redlich-Kister polynomials. The agreement among the reported data and other literature sources is analysed by comparing VmE, nDE, εrE and the deviation of c from mole-fraction linearity (Δc). The positive excess molar internal energies at constant volume (Um, VE) show the dominance of the breaking of interactions between like molecules in the energy balance on mixing, particularly the breaking of strong dipolar interactions between aniline molecules. This contribution is also dominant for the εrE values, as they are negative and decrease with the length of the alkan-1-ol chain. Calculations on the concentration-concentration structure factor are consistent with these statements, revealing homocoordination in the studied systems. The VmE are negative, which together with the positive Um, VE indicate the existence of important structural effects in the studied mixtures. The application of the Kirkwood-Fröhlich model shows that the average relative orientation of neighbouring dipoles is similar in the mixtures methanol + aniline or + pyridine, in spite of the different character of the predominant interactions in the latter mixture (heterocoordination).

Dielectric Properties of Binary Solvent Mixtures

Binary solvent mixtures exist as liquids over a wide range of temperatures and pressures. For the rational use of the solvent mixtures it is essential to know their physical properties as functions of their composition and the ambience. The excess functions of physical constants (X(sln)E) can be represented in the polynomial form of the molar fraction (x 2) of the cosolvent by the empirical Redlich-Kister equation.The equation clearly satisfies the condition that X(sln)E is zero at x 2 = 0 and at x 2 = 1. The physical constants of solutions include relative static permittivity, refractive index, viscosity, molar volume, vaper pressure, etc. The relative permittivity reflects the ease with which dielectric polarization proceeds. The relative permittivity is a measure of the solvent’s ability to insulate opposite charges from each other and has a very significant effect on the strength of the interactions between ions especially in dilute solutions. Electrostatic attractions and repulsions between ions are smaller in solvents with higher relative permittivities.We investigated the relative permittivities (ε r(sln)) and excess relative permittivities (ε r(sln)E) of binary mixtures of ethylene carbonate (EC) and a linear carbonate as a function of the composition at 25 ºC. The symbol x 2 denotes the molar fraction of the low-viscosity solvent: 2-fluoroethyl methyl carbonate (2FEMC), ethyl methyl carbonate (EMC), fluoromethyl methyl carbonate (FMMC), or dimethyl carbonate (DMC). EC is a cyclic carbonate, whereas 2FEMC, EMC, FMMC and DMC are linear carbonates. EC and EMC are commonly used as high-polarity and low-viscosity solvents, respectively, for lithium-ion batteries (LIB). Therefore, the relative permittivities of the binary mixtures decrease with an increase in x 2. a 0 is a dominant factor governing ε r(sln)E. a 0 may reflect the difference in the cooperative orientation polarization between the same and different types of dipoles. a 1 and a 2 may represent the difference in the contribution of the two components to the cooperative orientation polarization.The equations of the composition dependence of ε r(sln) and ε r(sln)E fitted experimental data. The ε r(sln) of the EC−2FEMC binary mixture was higher than that of the EC−EMC counterpart. The value of a 0 found in the EC−2FEMC binary solvent system (−49) was less negative than that in the EC−EMC binary solvent system (−51). These findings suggest that the amount of the cooperative orientation polarization of the EC−2FEMC binary mixture is larger than that found for the EC−EMC counterpart. The attraction between EC and 2FEMC molecules can be based on nonconventional weak intermolecular hydrogen bonding (CF−H···O or C−H···F−C). The weak hydrogen-bonding system does not exchange its proton and therefore it is no more a genuine hydrogen bond; it is an electrostatic attraction between positive charge on the hydrogen and negative charge on the organic fluorine or the organic oxygen. The characterization holds also for the EC−FMMC binary solvent system. The value of a 0 found in the EC−FMMC binary solvent system (−32) was also less negative than that in the EC−DMC binary solvent system (−41).The discussion of the composition dependence of ε r(sln) and ε r(sln)E is analogous to a positive deviation from Raoult's law. The positive deviation is characterized by vapor pressures that are higher than those calculated for an ideal solution. The ideal solution would show straight lines in a vapor pressure vs. composition diagram. The escaping tendencies of the components in the solution are accordingly higher than the escaping tendencies in the individual pure liquids. The effect has been ascribed to cohesive forces between unlike components that are smaller than those within the pure liquids, resulting in a trend away from complete miscibility. If the two liquids constituting the mixture are both nonpolar or if both are moderately polar, the positive deviations from ideal behavior are not large. On the other hand, if one component is slightly polar while the other is highly polar, considerable positive deviations may occur.