Kirkwood Correlation Parameter Research Articles

Chiral transfer from (1S, 2R, 5S)-(+)-menthol and its acetate to polar liquid crystal: Role of H-bond and dipole-dipole interaction

The mesomorphic and anisotropic properties of the induced chiral nematic phase in a mixture of substituted cyanobiphenyls (CB6) doped with chiral (1S, 2R, 5S) - (+) – menthol and its acetate are studied. The clearing temperatures and the pitch were measured, and the value of the helical twisting power β were calculated. An insignificant effect of chiral menthol, its racemate and acetate on the clearing temperature of the LC mixture, birefringence, and orientational ordering is shown. At the same time, the dielectric anisotropy of the helical phase CB6 + chiral dopant was found to strongly depend on the degree of mesophase twisting and the intensity of the magnetic field applied to the sample. Similar effects were shown in the study of kinematic viscosity. Based on the results of the Kirkwood's correlation parameter analysis and quantum-chemical calculations, it was shown that the introduction of the chiral mentol and menthyl acetate dopant leads to a change in the associative state of the LC matrix due to the formation of hydrogen bond of menthol and dipole-dipole contact of menthyl acetate with host molecules.

Orientational effects of h-bonding in the chirality transfer from (2R,3R)‑(−)‑2,3-butandiol to polar nematic liquid crystal

The dielectric and orientational properties of solutions of chiral (2R, 3R) - (−) 2,3‑butanediol and its racemic mixture in a liquid-crystalline mixture of alkoxycyanobiphenyls (CB6) were studied. The introduction of the chiral diol leads to the formation of a spiral nematic mesophase with the formation of a “fingerprints” texture. The introduction of dopants was shown to be accompanied by a decrease in the dielectric anisotropy of the mesophase. (2R, 3R) - (−) 2,3‑butanediol provides the most noticeable decrease as a result of chiral phase induction. From the NMR spectroscopy data, an increase in the ordering of the nematic phase during modification was observed. On the base of Kirkwood's correlation parameter analysis a change in associative state of the mesophase concerned with the formation of H-complexes alkoxycyanobiphenyl-butanediol was shown. By the of quantum chemical calculations, optimized structures of 1: 1 and 2:1 supermolecules were obtained, their dipole moments and 13C NMR spectra were calculated. By comparing these data with experimental spectra, a conclusion was made about the predominance of trimolecular complexes with hydrogen bond.

Dielectric, optical and orientational properties of liquid crystalline 4-alkyloxy-4′-cyanoazoxybenzenes and 4-alkyloxy-4′-cyanoazobenzenes

The influence of temperature on permittivity and refraction indices was studied for nematic liquid-crystalline 4-(n)alkyloxy-4′-cyanoazoxybenzenes and 4-(n)alkyloxy-4′-cyanoazobenzenes (n=4–6). The values of dielectric and optical anisotropy and orientational order parameter for nematic phase were calculated. The polarizability and dipole moments of molecules as well as their structures were calculated by DFT and AM1 methods. Kirkwood's correlation parameters were calculated as well. On the basis of experimental and calculated data the dielectric properties of mesogenic cyanoazoxybenzenes were shown to depend essentially on a mutual orientation of cyano group and NO bond of azoxy group, on a positional isomers ratio, and on an associative state.

Studies on molar volume, dielectric properties and refractive indices of Cyanex 923 + benzene/xylene at 300 K

The present investigation describes interactions between Cyanex 923 and benzene/xylene at 300K. The experimental values of molar volume, dielectric constant, refractive index, molar polarisation and molar refraction of pure Cyanex 923, benzene and xylene and their binary mixture over the entire mole fraction range have been determined. The excess parameters, Kirkwood correlation parameter, Gibb's free energy of mixing for these binary mixtures have been evaluated. The excess parameters have been tested using Redlich–Kister equation. The results indicate very weak interactions between Cyanex 923 and benzene/xylene.

Dielectric Studies of Binary Mixtures of 1-Propanol and Fluorobenzene

Complex permittivity spectra of 1-Propanol (1-PrOH), Fluorobenzene (FB) and their binary mixtures are obtained in radio and microwave frequency range using Vector network analyzer (VNA) operating in the frequency range 0.3 MHz to 3.0 GHz and standard microwave benches operated at 9.1 GHz and 19.61 GHz. Static dielectric constant (ε0) and high frequency limiting dielectric constant (ε∞1) for binary mixtures of 1-PrOH and FB are obtained by extrapolating the complex permittivity data towards low frequency side and high frequency side on complex plane plots. Optical dielectric constant (ε∞ = n2) for binary mixtures are measured using Abbe's refractometer. Excess static dielectric constant (ε0)E, Kirkwood correlation parameters (g, geff and gf) and Bruggeman factor (fB) are determined from the values of static dielectric constant (ε0) and optical dielectric constant (ε∞). These parameters have been discussed to explore the molecular interaction between the molecular species.

A Study of Molecular Interaction in Binary Mixtures of 1-Propanol with N,N-Dimethylformamide at Different Temperatures

The static dielectric constant (ε0) and optical dielectric constant (ε = n2) of binary mixtures of 1-Propanol (1-PrOH) with N,N-Dimethylformamide (DMF) of different concentrations, prepared by volume fractions (0.0, 0.1, . 1.0) are measured at 2 MHz using precision LCR meter and Abbes refractometer respectively at different temperatures. The excess dielectric constant (ε0)E, Kirkwood correlation parameters (geff, gF), Bruggeman parameter (fB) are evaluated. The variations of these parameters with concentration and temperature are discussed in terms of molecular interaction between the molecular species of constituting components in these mixtures.

EFFECT OF IMPURITIES ON THE DIELECTRIC PROPERTIES OF OLEIC ACID

Temperature dependence of the dielectric constant of oleic acid with different degrees of purity was measured in the 233–313 K range. It was observed that the presence of impurities (palmitic and linolenic acids) strongly influences the dielectric constant, melting point and dipole moment of the oleic acid. The values of apparent dipole moment and the Kirkwood correlation parameters were evaluated using the Kirkwood's model and were estimated to be about 1.20, 1.61 and 2.27 D, respectively for 60, 90 and 97 wt% oleic acid.

A study of dielectric properties and refractive indices of aniline + benzene, + toluene, + o-xylene, and + p-xylene at 298.15 K

The present study describes interactions between aniline + benzene, + toluene, + o-xylene, and + p-xylene mixtures at 298.15 K. The experimental values of refractive indices (n D) and dielectric constants (∈) of pure aniline, benzene, toluene, o-xylene and p-xylene and their binary mixtures over the whole composition range at 298.15 K have been obtained. Using these experimental data, the values of deviations in dielectric properties (∈ E), refractive indices (n D 2 E ), molar polarization (P E) of aromatic hydrocarbons in aniline have also been calculated and apparent molar polarization (P A), equilibrium constant (K), apparent dipole moment (µ app) and Kirkwood correlation parameter (g) for these mixtures have been evaluated further. The results indicate specific interactions between aniline and aromatic hydrocarbons, although more than one competing factors are responsible for these observed values of excess properties. The internal consistency of these functions have been tested using Redlich-Kister type equation.

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.

Dielectric and thermodynamic studies on a binary mixture of anisole with butyric or caprylic acid

The molecular interaction of anisole with fatty acids, such as butyric acid and caprylic acid, has been studied using standard dielectric methods. The permittivity at static and optical frequency (the sodium D-line) of a mixture of anisole + butyric acid and anisole + caprylic acid were measured at three different temperatures. Kirkwood correlation parameters, the excess permittivity, the Bruggeman parameter and excess free-energy were determined for each concentration of the mixture. A positive value of excess permittivity was obtained for the mixture of anisole + butyric acid, whereas for most concentrations of the anisole + caprylic acid mixture, the excess permittivity was negative at all studied temperatures. Negative and positive values of the Bruggeman parameters were obtained for the anisole + butyric acid and anisole + caprylic acid mixtures, respectively. Parallel and anti-parallel alignments of dipoles in the mixtures were identified.

Studies on molecular interactions and fluid structure of anisole with 2-ethyl-1-hexanol and decyl alcohol

The dielectric studies of a liquid can give information on its structure and interaction. Dielectric study of anisole has been carried out by mixing it with alcohols namely 1) 2-ethyl-l-hexanol and 2) decyl alcohol at different temperatures. The Kirkwood correlation factor, the excess dielectric permittivity, Bruggeman parameter and the thermodynamic properties of the mixtures have been determined and the results are interpreted. The interaction between like molecules is explained with the Kirkwood correlation parameter and the interaction between the unlike molecules is identified by the excess parameters and Bruggemann parameter. Values of Kirkwood correlation factor, excess static permittivity, Bruggeman parameter and the thermodynamic parameters are found to depend on the concentration and temperature of the mixtures. The parallel and anti-parallel orientations among the dipoles are analysed.

Refractive properties of binary mixtures containing 1,2-dichloroethane + 2-methoxyethanol or 1,2-dimethoxyethane

Refractive index (n) and related properties such as molar refraction (R) have been investigated for DCE + ME and DCE + DME binary mixtures over the entire composition range, at different temperatures in the interval 0 ≤ t/°C ≤ 70. Some empirical and theoretical relationships have been applied to study the dependence of the measured and derived quantities on temperature and on binary composition. Furthermore, the excess functions nE, RE and the excess Kirkwood correlation parameters Δg have been examined, in order to identify the presence of solvent-cosolvent adducts in these binary solvent systems. The results obtained have been interpreted on the basis of specific intermolecular interactions between different species.

Densities, Viscosities, Speeds of Sound, and Relative Permittivities for Methyl Acrylate + 1-Alcohols (C1−C6) at T = (308.15 and 318.15) K

Measurements of densities, viscosities, speeds of sound, and relative permittivities for five binary mixtures of methyl acrylate + 1-alcohols (methanol, 1-propanol, 1-butanol, 1-pentanol, and 1-hexanol) at T = (308.15 and 318.15) K are reported. The experimentally measured viscosities and speeds of sound in binary mixtures have been compared with those calculated using various semiempirical approaches. The isentropic compressibilities, molar electrical susceptibilities, and molar polarizations are calculated from the measured density, speed of sound, relative permittivity, and refractive index data. The excess volumes, excess isentropic compressibilities, excess molar electrical susceptibilities, and deviations in molar polarizations are calculated. These functions are fitted to a Redlich−Kister type equation. The variation of the Kirkwood correlation parameter has also been examined for all the binary mixtures over the whole composition range. Qualitative analysis of the various functions has been perfor...

Refractive Properties of Binary Mixtures Containing N,N- Dimethylformamide + 2-Methoxyethanol or 1,2-Dimethoxyethane

Refractive index (n) and related properties such as molar refraction (R) have been investigated for DMF + ME and DMF+DME binary mixtures over the entire composition range, at 15 different temperatures in the range 0 ≤ t/°C ≤ 70. Some relationships have been applied to study the dependence of the measured and derived quantities by temperature and composition. Furthermore, the excess functions n E, R E and the excess Kirkwood correlation parameters Δg have been examined, in order to identify the presence of solvent-cosolvent adducts in these binary mixtures. The results obtained have been interpreted on the basis of specific intermolecular interactions between different species.

Dielectric properties of mixtures of acetylene tetrachloride with toluene and acetone

Relative permittivities e are reported for binary liquid mixtures of acetylene tetrachloride (ATC) with toluene and acetone at 35°C. Measurements of refractive indices have also been made for the mixtures. The values of the quantity Δe, the deviations of the relative permittivities of these mixtures from ideality, have been calculated. The negative values of Δe obtained for ATC+ toluene mixtures may be explained as being due to a decrease in the degree of alignment of the molecular dipoles with changing composition of the mixture, whereas the positive values of Δe obtained for ATC+acetone mixtures are attributed to the formation of molecular complex between acetone and CHCl2CHCl2. The values of the Kirkwood correlation parameter g for both sets of mixtures have been calculated using the relative permittivity data.

Ultrasonic and dielectric behaviour of binary systems of quinoline with methylene chloride, chloroform, carbon tetrachloride, benzene and cyclohexane

Ultrasonic velocities, u, and isentropic compressibilities, κs, have been measured for binary mixtures of quinoline (C9H7N) with carbon tetrachloride (CCl4), benzene (C6H6) and chloroform (CHCl3) at 303.15 and 313.15 K, for mixtures of C9H7N with methylene chloride (CH2Cl2) at 293.15 and 303.15 K, and for mixtures of C9H7N with cyclohexane (c-C6H12) at 303.15 K. Measurements of relative permittivities, Iµ, and refractive indices, n, have also been made for binary mixtures of C9H7N with CCl4, CHCl3, CH2Cl2, C6H6 and c-C6H12 at 303.15 K. The quantities Δκs and ΔIµ which refer, respectively, to the deviations of the isentropic compressibilities and relative permittivities of the mixtures from the values arising from the mole-fraction mixture law, have been calculated. Δκs is negative throughout the whole range of composition in each case. ΔIµ is large and positive for mixtures of C9H7N with CHCl3 and CH2Cl2, practically zero at low mole fractions of C9H7N and small and positive for high mole fractions in the case of C9H7N–CCl4 and C9H7N–C6H6. For C9H7N–c-C6H12, ΔIµ is very slightly negative at low mole fractions of C9H7N and very slightly positive for high mole fractions. The Kirkwood correlation parameter, g, as calculated from the data on Iµ and n, for C9H7N–CHCl3 and C9H7N–CH2Cl2 was used to obtain Δg, which refers to the deviation of the Kirkwood correlation parameter of the mixture from the values arising from the mole-fraction mixture law. Δg is large and positive for these systems. The equilibrium constants Kf for the formation of a 1 : 1 complex of C9H7N with CHCl3 and CH2Cl2, as calculated from the relative permittivity data, are in accord with the theory of Barriol and Weisbecker, which is based upon the electrostatic interactions of the solute with the liquid. The apparent dipole moments, µapp, of C9H7N in CCl4 and C6H6 have been calculated. ΔIµ, Δg and Kf show that C9H7N forms strong complexes with CHCl3 and CH2Cl2, and that the interaction of C9H7N is stronger with CHCl3 than that with CH2Cl2. ΔIµ and µapp show that there is a specific interaction of C9H7N with CCl4 and C6H6, being stronger with CCl4 than that with C6H6.

Ultrasonic and dielectric behaviour of binary systems of methyl ethyl ketone with 1,2-dichloroethane, methylene chloride, trichloroethene, tetrachloroethene and cyclohexane

Measurements of ultrasonic velocity, u, and isentropic compressibilities, ks, have been made for binary mixtures of methyl ethyl ketone (MEK) with 1,2-dichloroethane (CH2ClCH2Cl), trichloroethene (CHClCCl2) and tetrachloroethene (CCl2CCl2) at 303.15 and 313.15 K, for mixtures of MEK with methylene chloride (CH2Cl2) at 293.15 and 303.15 K, and for mixtures of MEK with cyclohexane (c-C6H12) at 303.15 K. Measurements of relative permittivities, Iµ, and refractive indices, n, have also been made for binary mixtures of MEK with CH2Cl2, CH2ClCH2Cl, CHClCCl2, CCl2CCl2 and c-C6H12 at 303.15 K. The quantities Δks and ΔIµ which refer, respectively, to the deviations of the isentropic compressibilities and relative permittivities of the mixtures from the values arising from the mole fraction mixture law, have been calculated. Δks is positive for mixtures of MEK with c-C6H12 and CH2Cl2, and negative for mixtures of MEK with CH2ClCH2Cl, CHClCCl2, and CCl2CCl2, whereas ΔIµ is positive for mixtures of MEK with CH2Cl2, CH2ClCH2Cl and CHClCCl2, and negative for its mixtures with CCl2CCl2 and c-C6H12. Δg refers to the deviations of the values of the Kirkwood correlation parameter, g, for mixtures from the values arising from the mole fraction mixture law (as calculated from the data for Iµ and n for mixtures of MEK with CH2ClCH2Cl and CH2Cl2); values of Δg have been found to be positive. The values of Δks, ΔIµ and Δg for the various systems show that MEK forms molecular complexes with CH2Cl2, CH2ClCH2Cl, CHClCCl2 and CCl2CCl2. The values of the equilibrium constant Kf for the formation of 1:1 complexes of MEK with CH2ClCH2Cl and CH2Cl2, as calculated using the relative permittivities, are in accord with the theory of Barriol and Weisbecker. The values of the dipole moments of MEK in CCl2CCl2 and c-C6H12 also indicate a specific interaction of MEK with CCl2CCl2.

Dielectric relaxation in non-aqueous solutions. Part 5.—Propylene carbonate (4-methyl-1,3-dioxolan-2-one)

The permittivity (Iµ′) and loss (Iµ″) of propylene carbonate (4-methyl-1,3-dioxolan-2-one) have been measured at several temperatures between 0° and 50°C in the frequency range 0.5 to 35 GHz. The overall frequency response of the complex permittivity is unsymmetrical but can be satisfactorily represented by the equation Iµ′(ω)– iIµ″(ω)=Iµ∞+(Iµs–Iµ∞)/(1 + iωτ0)ξ.The temperature dependence of the relative static permittivity (Iµs) is accurately described by the empirical relation, Iµs=A exp(–LT), with A= 195.6 and L= 3.681 × 10–3 K–1, although the dielectric relaxation times (τ0) do not fit the usual Arrhenius expression. The distribution parameter (ξ) and high frequency limiting permittivity (Iµ∞) both vary in an irregular manner with increasing temperature. Propylene carbonate also absorbs in the far infra-red between 20 and 170 cm–1 with a maximum absorption at about 70 cm–1.Values of the Kirkwood correlation parameter (g) calculated from Iµs indicate that short range order is not significant in liquid propylene carbonate. The unsymmetrical frequency response of (Iµ′– iIµ″) has been discussed in terms of current molecular theories.

Dielectric properties of glycerol in the range 0.1–105Hz, 218–357 K, 0–53 kb

The dielectric constant and loss of glycerol has been measured in the range 0.1–105 Hz, 218–357 K, and 0–53 kb. A piston-cylinder apparatus was used for the range 0–25 kb and an anvil apparatus for the range 25–53 kb. The static dielectric constant increases with increasing density at a rate that indicates that ∂ln gµ20/∂ ln ρ, where g is Kirkwood's correlation parameter, µ0 the dipole moment of an isolated molecule, and ρ the density, is –0.2. The dispersion region broadens with increasing pressure, and a high-frequency dispersion can be resolved at the higher pressures and lower temperatures. The frequency of maximum loss ƒm decreases with increasing pressure at an increasing rate, a behaviour which is clearly related to the approach to the glass transition. Isotherms can be fitted to the equation ln ƒm=A–B/(p0–P) where A, B and p0 are constants and p0 is the pressure at which ƒm extrapolates to zero.

CII. The high temperature susceptibility of a lattice of permanent dipoles

Summary Pople's recent criticism of the results obtained, for the high temperature susceptibility of a permanent dipole lattice, by Van Vleck and by Rosenberg and Lax is shown to be unjustified. Two alternative derivations are given of the relations obtained by Van Vleck et al. It is shown that Kirkwood's correlation parameter, g. depends upon dipole-dipole interactions.