Viscoelastic studies of some phenols from dielectric measurements

The variation of dielectric relaxation time with the viscosity of the medium is being exploited in drawing certain quantitative conclusions regarding molecular motion and intermolecular forces in liquids, liquid mixtures, dilute solutions and multi-component polar solutes in dilute solution. With no perfect empirical or theoretical equation in place for the variation of dielectric relaxation time with viscosity, the experimental investigations on different systems only can give an insight. In the present study the results of dielectric measurements carried out on pure samples of o-ethyl phenol, 2-n-butylphenol, 4-n-butylphenol, and 2,6-butylphenol in dilute solutions in different mixed solvents (benzene?+?paraffin) and on binary mixtures (1?:?1) of p-2-n-butylphenol?+?4-n-butylphenol and p-bromonitrobenzene?+?2,6-butylphenol, are reported. For comparison, the results on p-bromonitrobenzene?+?m-bromonitrobenzene as an example of mixture of non-associative liquids was also carried out and the results are presented. Different parameters determined using these dielectric measurements are also presented using different models and these studies indicate that the dielectric behavior at microwave frequencies favor the concept of dynamic viscosity and a single viscoelastic relaxation time for the system under study.     

Dielectric relaxation studies of binary mixtures of N-methylacetamide and N-methylformamide in benzene solutions using microwave absorption data

Using standard microwave X-band technique and by following Gopala Krishna's single frequency (9.90?GHz) concentration variational method, the dielectric relaxation times (τ) and the dipole moments (μ) of dilute solution of N-methylacetamide (NMA), N-methylformamide (NMF) and NMA?+?NMF binary mixtures in benzene solutions have been calculated at different temperatures. The energy parameters for the dielectric relaxation process for NMA?+?NMF binary mixture containing 30?mol% NMF have been calculated at 25, 30, 35 and 40°C and compared with the corresponding viscosity parameters. A good agreement between the free energy of activation from these two sets of values shows that the dielectric relaxation process like the viscous flow process can be treated as the rate process. From relaxation time behavior of NMA and NMF binary mixture in benzene solution, solute–solute types of the molecular association has been proposed.     

Correspondence between Grunberg-Nissan,Arrhenius and Jouyban-Acree parameters for viscosity of 1,4-dioxane + water binary mixtures from 293.15 K to 320.15 K

The study of physical properties of binary liquid mixtures is of great importance for understanding and characterisation of molecular interactions. In the same way, some models attempt to correlate viscosity in liquid mixtures to release eventual interactions, structures’ change and peculiar behaviours. Grunberg–Nissan (GN) parameters for viscosity (η) in 1,4-dioxane?+?water mixtures over the entire range of mole fractions under atmospheric pressure and from 293.15?K to 320.15?K were calculated from experimental dynamic viscosities presented in previous works. Many experimenters investigate physicochemical properties using numerous models to derive some interpretations and conclusions. The present work comes within the framework of correlating different used equations to restrict investigations with an optimal of number of these models. Relationship between the GN, Arrhenius and Jouyban–Acree parameters for viscosity is shown in one binary mixture which dielectric constants of their pure components are very distinct.     

Molecular interaction studies in hydrogen bonded polar binary mixtures

The molecular interactions between the polar systems of propan-1-ol (1PN) with alkyl benzoates (methyl benzoate and ethyl benzoate) for various mole fractions at different temperatures are studied by determining the dielectric permittivity in radio, microwave and optic frequency regions, respectively. Dipole moment, excess dipole moment, excess Helmholtz free energy, excess permittivity, relaxation time, excess inverse relaxation time and excess thermodynamical values are calculated using experimental data. Hamiltonian quantum mechanical calculations are performed on both pure and equimolar binary systems of 1PN with alkyl benzoates for the measurement of dipole moment from the ab initio Hartree–Fock and density functional theory (B3LYP) methods with 6-31?+?G* and 6-311?+?G** basis sets using Spartan 08 modelling software and these theoretical values are in good agreement with the experimental values.     

Mutual macromolecular crowding as the basis for polymer solution non‐ideality

Semidilute polymer solutions differ greatly from dilute solutions in properties such as viscosity, relaxation time, elastic modulus, colloid osmotic pressure, and light scattering. Previously, Matsuoka and Cowman proposed a single semiempirical expression for the nonideality contribution due to the concentration and intrinsic viscosity dependence, which has no other adjustable parameters, but quantitatively fits data for flexible, semiflexible, and rigid polymers in good solvents. In this report, the excluded volume theory as proposed by Ogston and Laurent is generalized to include mutual crowding between identical polymers based on hydrodynamic volumes, and applied to derive the expression for the nonideality contribution to specific viscosity, colloid osmotic pressure, and light scattering. Additionally, consideration of the contribution of mutual macromolecular crowding to the effective solvent viscosity allows prediction of polymer relaxation time and elastic modulus in semidilute solutions. This theoretical approach now allows the prediction of semidilute polymer solution properties based only on concentration and intrinsic viscosity, and conversely allows intrinsic viscosity (and thus average molecular weight) to be calculated from measurements made on semidilute solutions of known concentration. Copyright © 2016 John Wiley & Sons, Ltd.     

Studies on solution properties of ternary mixture of acetophenone + n-amyl alcohol + dichloromethane and its corresponding binaries at 298.15 K

The excess values of molar volume (V ^E), viscosity deviation (Δη), deviation in isentropic compressibility (ΔK_S ), excess molar refraction (ΔR) and excess Gibbs energy of activation (ΔG^*E ) of viscous flow have been investigated from the experimentally measured densities, viscosities, sound speeds and refractive indices for three binary mixtures of acetophenone?+?n-amyl alcohol, acetophenone?+?dichloromethane and n-amyl alcohol?+?dichloromethane and their corresponding ternary mixtures at 298.15?K over the entire composition range. The calculated quantities are further fitted to the Redlich–Kister equation to estimate the binary fitting parameters and standard deviations from the regression lines. The excess or deviation properties were found to be either negative or positive depending on the molecular interactions and the nature of liquid mixtures and have been discussed in terms of molecular interactions and structural changes.     

Viscometric and volumetric properties of benzene + methyl acetate,or + methyl propanoate,or + methyl butanoate binary systems at 283.15, 298.15 and 313.15 K

Viscosities and densities of three binary liquid mixtures, benzene?+?methyl acetate, benzene?+?methyl propanoate and benzene?+?methyl butanoate, have been measured at 283.15, 298.15 and 313.15?K, and atmospheric pressure. From experimental data, viscosity deviation, excess energy of activation for viscous flow, and excess molar volume were calculated and satisfactorily correlated with Redlich and Kister equation. Empirical and semiempirical equations and the predicted group-contribution method, universal automatic computer, were applied.     

聚乙烯接枝马来酸酐极稀和稀溶液性质的研究

该文研究了聚乙烯接枝马来酸酐 (PE g MAH)在极稀和稀浓度范围内的溶液行为 .两个区间内的粘浓关系都呈直线关系 ,但极稀区间的斜率比稀浓度的大得多 .两者的交点C 为临界接触浓度 .随着接枝率的增大 ,比浓粘度逐渐增大 .温度升高也使比浓粘度增大 .     

Dielectric and visco-elastic properties of laterally fluorinated liquid crystal single compounds and their mixture

The physical properties of three laterally fluorinated liquid crystalline compounds with negative dielectric anisotropy have been studied from static dielectric permittivity, optical birefringence, bend elastic constant, relaxation time and rotational viscosity measurements. Such negative dielectric anisotropy materials find use as components of mixtures for application in vertically aligned mode liquid crystal displays. Moreover, the physical properties of one phenyl cyclohexane compound with positive dielectric anisotropy have also been studied. A five-component mixture comprising these four mesogens and a non-mesogenic component has been formulated and its physical properties have been thoroughly investigated. An attempt has been made to strike a balance between the optical birefringence of the mixture to adjust the cell gap and the dielectric anisotropy and threshold voltage (V_th ) to ensure low driving voltages. The pretilt angle effect on the threshold voltage and the relaxation time has also been studied. At T?=?20°C, the response time decreases to 22% and 41% for the mixture for 2° and 5° pretilt as compared to zero pretilt. On the other hand, at the same temperature the V_th values are decreased by 5% and 9%, respectively.     

Identification of dielectric and structural relaxations in glass-forming secondary amides

Dielectric relaxation dynamics of secondary amides is explored in their supercooled state near the glass transition temperature Tg by investigating N-ethylacetamide and its mixtures with N-methylformamide. All the samples are found to exhibit giant dielectric permittivities, reaching over 500 in N-methylformamide-rich mixtures around Tg. For both the neat and binary systems, the predominant relaxation peak is of the Debye-type throughout the viscous regime, which is an unexpected feature for a glass former with intermediate fragility. The present results combined with the earlier reported high-temperature data reveal that the dielectric strength delta epsilon(D) of the Debye relaxation extrapolates to zero at frequencies of 10(10)-10(11) Hz, which is about two orders of magnitude lower than the phonon frequency limit typical of the structural relaxation. This Debye process is remarkably similar to the dielectric behavior of many monohydroxy alcohols, which implies a common nature of purely exponential relaxation dynamics in these liquids. Based on the dielectric properties, we conclude that the Debye relaxation in the secondary amides is not a direct signature of the primary or alpha-relaxation, the latter being obscured at low temperatures due to the relatively low permittivity and close spectral proximity to the Debye peak. As in the case of monohydroxy alcohols, dielectric polarization and structure fluctuate on different time scales in secondary amides. The Kirkwood-Fr?hlich correlation factors for Debye-type liquids are also discussed.     

Viscosity enhancement of complexed solutions formed through the complexation of nonionic water‐soluble polymers with chemically complementary structures in aqueous media

The intermacromolecular complexation of polymers with chemically complementary structures in aqueous media is a new approach to modifying polymer solutions, especially to enhance solution viscosity. In this study, complexed solutions formed through the hydrogen‐bonding complexation of several nonionic water‐soluble polymer pairs—poly(acrylic acid) (PAA) with polyacrylamide (PAM), PAM with poly(ethylene oxide) (PEO), PAA with poly(vinyl alcohol) (PVA), and PEO with PVA—were prepared, and the viscosity enhancement of the complexed solutions were studied with vision spectrophotometry and viscometry. The effects of the polymer concentration, polymer molecular weight, and pH value of the polymer solution on the intermacromolecular interactions were investigated through a comparison of the viscosity enhancement factor R of different complexed solutions. The results show that the viscosity of the PAA/PAM complexed solution is much higher than that of its constituents, whereas that of the PAM/PEO and the PAA/PVA complexed solutions are between the viscosities of their constituents but are higher than the theory values calculated from the blending rule of two polymer solutions. These results indicate that in the complexed solutions there exist interactions between the macromolecules with chemically complementary structures, although the interactions are quite different for the different complexed systems. It is the interactions that lead to an association of the polymers and, hence, an obvious enhancement in the solution viscosity and the resistance of the polymer solutions to shearing. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1069–1077, 2000     

The Dipole Moment and Molecular Mobility of Cholesteryl-Containing Monomers in Solution: Association and Gel Formation

The permittivity, molecular dipole moment, and dielectric relaxation parameters (relaxation time and activation energy) of cholesteryl esters of alkyl-, methacryloyl-ω-oxy-, and aminocarboxylic acids were studied in dilute solutions in toluene. The influence of the chemical structure of molecules on these characteristics was considered. The presence of NH groups and cholesteryl radicals (responsible for H-bonding and specific dispersion interactions) and an increase in the length of methylene chains in molecules substantially influenced dipole moments and dipole polarization relaxation times and contributed to the development of structuring processes (association and gel formation) in solutions of these compounds.     

Influence of temperature on thermodynamic properties of acid–base liquid mixtures

Ultrasonic velocity, u density, ?? and viscosity, ?? of mixtures of N,N-dimethyl acetamide with equimolar mixture of ethanol?+?isopropyl alcohol/isobutyl alcohol/isoamyl alcohol, including those of pure liquids over the entire composition have been measured at T?=?308.15, 313.15, and 318.15?K. Using this data, various thermo-acoustic parameters such as deviations in ultrasonic velocity, ?u, isentropic compressibility, ?k _s , viscosity, ????, excess molar volume, $ V_{\text{m}}^{\text{E}} $ and excess Gibb??s free energy of activation for viscous flow, ??G ^*E have been calculated at different temperatures. The calculated deviation and excess functions have been fitted to the Redlich?CKister type polynomial equation. The influence of temperature on the observed negative and positive values of deviation and excess thermodynamic properties has been explained in terms of molecular interactions present in the investigated acid?Cbase liquid mixtures. The experimental data of ultrasonic velocity have been used to check the applicability of velocity models of Nomoto, Van Dael and Vangeel and Junjie and viscosity data have also been availed to test the applicability of standard viscosity models of Grunberg-Nissan, Hind-Mc Laughlin, and Katti-Chaudhary for all the systems investigated at various temperatures.     

Viscosity of aqueous solutions of 2-propyne-1-ol, 2-methyl-3-butyne-2-ol and 3-butene-2-ol

Viscosities of aqueous solutions of 2-propyne-1-ol (propargyl alcohol), 2-methyl-3-butyne-2-ol and 3-butene-2-ol have been measured at temperatures 308.15, 313.15, 318.15, 323.15 and 328.15?K over the entire composition range. Viscosity of the aqueous solutions of 2-methyl-3-butyne-2-ol and 3-butene-2-ol increases up to a maximum value and then starts decreasing almost linearly as the mole fraction of alcohol increases. 2-Methyl-3-butyne-2-ol + water and 3-butene-2-ol + water systems exhibit maxima around 0.5 and 0.2 mole fraction, respectively. Conversely, 2-propyne-1-ol + water system shows a rapid initial increase in viscosity up to 0.3 mole fraction followed by a slow steady increase as the mole fraction of alcohol increases to its pure state. Plots of excess viscosities against mole fraction of organic solutes for all the systems exhibit a sharp increase in η ^E to reach a well defined maxima, after which the curves show a descending trend. The variations of viscosity and excess viscosity with the composition of the mixtures have been interpreted in terms of hydrophobic and hydrophilic interactions between the species forming the mixtures.     

Normal stress and shear stress in a viscoelastic liquid under steady shear flow: Effect of molecular weight heterogeneity

Under steady shear flow, the normal stress and the shear stress in both dilute and concentrated solutions of monodisperse poly-α-methylstyrenes and their blends were measured. It was confirmed that the molecular theories of Rouse and Zimm extended to concentrated solutions can explain the relation between the zero-shear normal stress coefficient and the zero-shear steady-flow viscosity for both monodisperse and polydisperse systems. Shear-rate dependence of steady-flow viscosity can be understood fairly well by the molecular entanglement concept proposed by Graessley so long as the polymer is monodisperse or the amount of the higher molecular weight component is high. However, zero-shear viscosity of blended systems cannot be explained quantitatively by the theory of Graessley. The shear-rate dependence of steady-state compliance of blended systems was also observed, and it can well be explained by the theory of Tanaka, Yamamoto, and Takano which interpreted the shear rate-dependent steady-state compliance in terms of the relaxation time spectrum and its variation with shear rate.     

Acoustic and volumetric studies of uracil in aqueous urea solution at different temperatures

Volumetric, viscometric and ultrasonic studies of uracil in an aqueous urea solution in varying concentration of 2, 3 and 5?M have been carried out at 298, 308 and 318?K. The uracil concentration in the aqueous urea solution varies from 0.05% to 0.4%. Density (ρ), viscosity (η) and sound speed (u) have been measured. The experimental data are used for computing various thermodynamic and acoustic parameters, namely apparent molar volume, isentropic compressibility, apparent isentropic compressibility, relative association, intermolecular free length, acoustic impedance, viscous relaxation time, hydration number, Gibb's free energy, classical absorption coefficient of the solution and viscosity data have been further analysed in the light of Masson's equation and Jones–Dole's equations, respectively. The results have been discussed in terms of solute–solute and solute–solvent interaction and the structural changes of the solutes in solutions. The effect of variation of temperature on these interactions has also been investigated.     

Correspondence Between Grunberg–Nissan, Arrhenius and Jouyban–Acree Parameters for Viscosity of Isobutyric Acid?+?Water Binary Mixtures from 302.15 to 313.15?K

The study of physical properties of binary liquid mixtures is of great importance for understanding and characterizing intermolecular interactions. Similarly, some models attempt to correlate viscosity in liquid mixtures in order to illuminate interacting structures and peculiar behaviors. Grunberg?CNissan parameters for viscosity (??) in isobutyric acid?+?water mixtures over the entire range of mole fractions under atmospheric pressure and from 302.15 to 313.15?K were calculated from experimental dynamic viscosities presented in previous works. Many experimenters investigate physicochemical properties using various models to develop interpretations and conclusions. The present work comes within the framework of correlating different equations. Relationships between the Grunberg?CNissan and Arrhenius and Jouyban?CAcree parameters for viscosity are shown in one critical binary mixture.     

Dielectric spectra broadening as the signature of dipole-matrix interaction. I. Water in nonionic solutions

Whenever water interacts with another dipolar entity, a broadening of its dielectric relaxation occurs. Often this broadening can be described by the Cole-Cole (CC) spectral function. A new phenomenological approach has been recently presented [A. Puzenko, P. Ben Ishai, and Y. Feldman, Phys. Rev. Lett. 105, 037601 (2010)] that illustrates a physical mechanism of the dipole-matrix interaction underlying the CC behavior in complex systems. By considering the relaxation amplitude Δε, the relaxation time τ, and the broadening parameter α, one can construct a set of 3D trajectories, representing the dynamic behavior of different systems under diverse conditions. Our hypothesis is that these trajectories will contribute to a deeper understanding of the dielectric properties of complex systems. The paper demonstrates how the model describes the state of water in aqueous solutions of non-ionic solutes. For this purpose complex dielectric spectra for aqueous solutions of D-glucose and D-fructose are analyzed.     

Rheological properties of associates of ionic monomers with micelles of oppositely charged surfactants

Rheological properties of associates formed by interaction of trimethyl[methacryl-oxyethyl]ammonium methyl sulfate with sodium octyl- and dodecyl sulfate micelles, as well as associates of sodium 4-styrenesulfonate with dodecyltrimethylammonium bromide micelles in aqueous solutions were studied by steady shear and oscillatory (dynamic) shear measurements with Fourier transform. It was shown that viscosity depends on the composition and achieves maximum value at equimolar ratio of components for two of studied systems. The extremal dependence of the viscosity vs. composition is not observed for systems with sodium octyl sulfate due to weak interactions between the components. The systems exhibiting the anomalous dependencies of concentration to viscosity are viscoelastic fluids due to the physical entanglements between the associates.     

Volumetric and viscosity properties of {propyl propanoate (1) + heptane (or octane) (2)} mixtures at several temperatures and correlation with the Jouyban–Acree model

Densities and viscosities of binary liquid mixtures of propyl propanoate + heptane and propyl propanoate + octane at temperatures of 278.15, 283.15, 288.15, 293.15, 298.15, 303.15, 308.15, 313.15, 318.15 and 323.15 K have been measured at atmospheric pressure over the entire range of composition. Using these experimental data, the excess molar volumes and the viscosity deviation have been calculated. The experimental data of density and viscosity at different investigated temperatures were mathematically represented by the Jouyban–Acree model. The mean relative deviation (MRD) was used as an error criterion, and the MRD values for data correlation of density and viscosity at different investigated temperatures are less than 0.03% and 0.50%, respectively. Excess molar volumes and viscosity deviations were correlated with Redlich–Kister equation. The calculated data point out the absence of speci?c interactions between the molecules of different components, which would be slightly weaker compared to the interactions in the pure components.