Activation Parameters Of Viscous Flow Research Articles

Solvation behavior of chitosan monomers in aqueous [Hmim]CL solutions. Experimental and DFT studies

This paper reports densities and viscosities for the mixtures of D-glucosamine hydrochloride (GlcN·HCl) and N-acetyl-D-glucosamine (GlcNAc) with aqueous solutions of 1-hexyl-3-methylimidazolium chloride, [Hmim]Cl, between 293.15 and 318.15 K in 5 K increments and atmospheric pressure. Leveraging this data, we calculated volumetric properties such as apparent molar volume, Vϕ, limiting partial molar volume, Vϕ0, and standard molar volume of transfer, ΔVϕ0. We handled viscosity data to compute the viscosity B-coefficient and several activation parameters of viscous flow. Some of these are relevant in discussing interactions between monosaccharides (solute) and [Hmim]Cl (co-solvent) in aqueous media. The solute–solvent interactions were discussed based on ionic/ hydrophilic/ hydrophobic interactions using the co-sphere overlap model. ΔVϕ0 > 0 indicates that ionic/hydrophilic interactions predominate in the studied systems and are stronger in GlcN·HCl solutions than in GlcNAc at low [Hmim]Cl molalities. At higher [Hmim]Cl concentrations, decreasing values of ΔVϕ0 suggest the dominance of hydrophobic interactions over hydrophilic/ionic ones. We discuss (using Hepler’s constant and viscosity B-coefficient) the ability of monosaccharides to act as structure maker/breaker in aqueous [Hmim]Cl solutions. This indicates that GlcNAc is a better structure promoter than GlcN⋅HCl in aqueous [Hmim]Cl solutions. Finally, density functional theory (DFT) was used to model the molecular structure and compute the solute–solvent interaction energies using the GAMESS 2016 software.

Activation parameters of viscous flow of guar gum and its cross-linked system

The structure of a cross-linked form of a concentrated solution of guar gum was studied using IR spectroscopy. The processes of viscous flow of concentrated solutions of guar gum and its cross-linked system have been studied. It is shown that this system is a non-Newtonian fluid with a thixotropic type of viscous flow anomaly, which is also determined by the nature of the complexing agent. The influence of temperature on viscous flow processes, as well as the structure of aqueous systems of guar gum and its cross-linked form, were studied based on the average statistical sizes of kinetic units, which makes it possible to estimate the mobility of structural elements and their sizes for concentrated systems. The activation parameters of the viscous flow of aqueous systems of guar gum and its cross-linked system were studied. Calculations of thermodynamic parameters were carried out free energy, heat of activation of viscous flow, characterizing the strength of structures, and entropy of activation of viscous flow, characterizing the ordering of structures. At high shear stresses, for the guar gum solution system, the processes of ordering and orientation prevail during flow, and for the guar gum - pentaerythritol borate system, the processes of structure destruction and disordering prevail.

Thermodynamic characterization of aqueous solutions of NaCl, KCl, MgCl2 and CaCl2: volumetric, acoustic, viscometric and computational analysis

The volumetric and acoustic properties of alkali and alkaline earth metal salts are ubiquitous in numerous biological and non-biological processes and accurate formulation of their thermophysical properties is a fundamental prerequisite for complete exploration of their diverse applications. To meet this purpose, in this investigation, we herewith report the systematic data of densities ρ, speed of sound u and viscosity η of aqueous binary solutions of the prominent alkali and alkaline earth metal salts viz. NaCl, KCl, MgCl2, and CaCl2 at seven different temperatures T = (288.15–318.15 K) and ambient pressure over the wide concentration range of (0.002–1) mol∙kg−1.These experimental data have been further employed to obtain some important thermodynamic parameters, viz, the apparent molar volume of solute Vϕ, limiting apparent molar volume of solute Vϕ0, isentropic compressibility of solution κS, apparent molar isentropic compression of the solute KS,ϕ, limiting apparent molar isentropic compression of solute KS,ϕ0 and apparent molar expansibility Eϕ0. Further, the coefficient of thermal expansion α*, the second-order derivative of limiting apparent molar volume ∂2Vϕ0/∂T2, Jones-Dole equation viscosity A, B, D coefficients, temperature derivative of B coefficient i.e. dB/dT, activation parameters for viscous flow and hydration number nH have also been computed. The results obtained have been used to elucidate different interactions taking place in the aqueous electrolytic solutions. To corroborate the experimental results, quantum chemical calculations were performed using density functional theory (DFT) by Gaussian software package. The calculations included an analysis of molecular orbitals, with particular emphasis on the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO).

Influence of physicochemical properties and structure of mixed solvents propylene glycol – macrogol 400 on their in vitro release

Aim. To study the density and dynamic viscosity of the mixed solvents propylene glycol (PG) – macrogol 400 (M400), to calculate their excess values and excess activation parameters of viscous flow, to evaluate the features of the structure of the mixed solvents and its influence on the in vitro release of PG and M400.
 Materials and methods. The mixed solvents PG - M400 were studied over the entire concentration range at temperatures from 293.15 to 313.15 K. The density and dynamic viscosity were determined, and the excess density, excess dynamic viscosity, activation parameters of viscous flow, and excess activation parameters of viscous flow were calculated. The in vitro release of PG and M400 from the mixed solvents was studied using vertical diffusion cells. The content of PG and M400 in the receptor medium was determined by gas chromatography using validated analytical procedures. The release rate, cumulative content, percentage of released PG or M400, coefficients of correlation and coefficients of determination were calculated.
 Results. The isotherms of excess density and excess dynamic viscosity of the mixed solvents PG-M400 pass through a maximum. The enthalpy makes the main contribution to the free activation energy of the viscous flow. The excess free energy is positive and has small values; the values of the excess entropy and excess enthalpy are negative, and the isotherms have the minimum at PG concentrations of 70‑75mol %. The release parameters of M400 are greater in binary mixtures where the M400 structure predominates. At PG content of ~75 mol %, the release parameters for PG and M400 are identical. With the increase in PG content above 75 mol %, when the PG structure predominates in the system, the release parameters of PG increase dramatically, and the release parameters of M400 decrease sharply.
 Conclusions. The structure of the binary system PG – M400 depends on its composition. Based on the isotherms of excess activation of viscous flow, it is possible to differentiate the areas where the structure of PG or the structure of M400 dominates, or the mixed structure of the binary solvent prevails. The in vitro release parameters for PG and M400 depend on the structure of the mixed solvents. The greatest difference in the release parameters of PG and M400 was observed in the area where the structure of PG dominates

Molecular interactions of two biologically active molecules (L–serine and L-valine) in aqueous [Hmim]Cl solutions: Volumetric and viscometric approach

Mixtures of amino acids L–serine and L–valine + (0.05, 0.1, 0.2 and 0.3 mol·kg−1) aqueous solutions of ionic liquid 1-n-hexyl-3-methylimidazolium chloride, [Hmim]Cl, at temperatures T = (293.15, 298.15, 303.15, 308.15 and 313.15 and 318.15 K) have been studied using density and viscosity measurements. From density, the volumetric properties: the apparent molar volume, Vϕ, limiting partial molar volume, Vϕ0, and expansibility, Eϕ0, standard molar volume of transfer, ΔVϕ0, and hydration number, nH, were calculated. Similarly, from viscosity measurements and using the Jones–Dole equation and transition state treatment, the viscosity B coefficient and some activation parameters of viscous flow were calculated. These parameters, their variation with temperature and concentration, were discussed in terms of transition state theory. Based on the co-sphere overlap model, the solute–solute and solute–solvent interactions were discussed, including amino acids hydration, and structural effects. The structure making/breaking ability of the amino acids in solutions was also discussed using Hepler's constant and (dB/dT) variation.

Viscometric and Densimetric Study of Water–PEG–KBr Systems

The dynamic viscosity and density of a water–PEG–KBr system are measured in the ranges of 293.15–323.15 K and 0–0.001 mol parts. Polyethylene glycol samples with average molecular weights of 1000, 1500, 3000, 4000, and 6000 g/mol are used. The concentration of KBr is 0.01 mol parts. The activation parameters of viscous flow (Gibbs energy, enthalpy, and entropy) and the partial molar volume of PEG in a solution are calculated using experimental data in the specified range of temperatures and concentrations. It is shown that the activation parameters of viscous flow grow along with concentration and molar weight. It is found that the partial molar volume of PEG in a solution falls as the concentration rises, and the partial molar volume per monomer does not change, depending on the average molecular weight of PEG. A simple way of determining the hydration number of a polymer molecule is described, based on which the hydration number of a PEG macromolecule in a solution is calculated. It is found that the hydration number of a PEG macromolecule falls as the temperature rises and grows along with the molecular weight.

Theoretically consistent calculation of viscous activation parameters through the Eyring equation and their interpretation

The activation parameters of viscous flow can be used to probe the molecular interactions in fluids from viscosity experimental data. They are assessed by mathematical derivations of the Eyring equation, but differences in these derivations can generate parameters that lead to conflicting interpretations. In this work, a new method for the estimation of the activation parameters of viscous flow is proposed and compared with two other methods previously reported in the literature. It is shown that the new method is the only presenting theoretically consistent trends, as confirmed by its application to alkanes and ionic liquids.

Molecular interactions of drug semicarbazide hydrochloride in aqueous-D-xylose/L-arabinose solutions at different temperatures: Volumetric, acoustic and viscometric study

The interactions of drug semicarbazide hydrochloride in water and in aqueous-carbohydrate (D-xylose/L-arabinose) solutions from their physicochemical behaviour are studied. Density, ρ, ultrasonic speed, u and viscosity, η of the drug semicarbazide hydrochloride in water and in aqueous-D-xylose/L-arabinose (5 wt% and 10 wt% of D-xylose/L-arabinose in water, w/w) solvents were measured as functions of concentrations at temperatures, T = (293.15 – 318.15) K and at atmospheric pressure, p = 101 kPa. The measured data have been utilized to calculate various properties like the apparent molar volume, Vφ from density measurements while apparent molar compressibility, Ks,ϕ, acoustic impedance, Z and intermolecular free length, Lf from ultrasonic speed measurements. The values obtained from these parameters indicate strong solute–solvent interactions within the solutions. The viscosity data have been analyzed using Jones-Dole equation and coefficients A and B were evaluated. The temperature derivative of B-coefficient, dB/dT together with activation parameters of viscous flow have also been determined. The results are discussed in terms of hydrophilic-hydrophilic and hydrophilic-hydrophobic interactions in these systems along with the structure breaking/making ability of the drug.

Viscosity measurements of the binary mixture ethyl lactate+acetonitrile from 283.15 to 323.15 K. Activation parameters and their connection with molecular interactions

ABSTRACT Experimental viscosity data were obtained for ethyl lactate + acetonitrile mixtures at five temperatures. Viscosity deviations and activation parameters of viscous flow have been calculated. Values obtained suggest that the inter and intramolecular hydrogen bonds of ethyl lactate are affected by the electron pair in the nitrogen atom of acetonitrile. The obtained data have been correlated through several approaches proposed in the literature, namely, the Grunberg – Nissan, the Katti – Chaudri, the Teja – Rice, and the Herráez approaches of, for dynamic viscosities.

Investigation of electrolytes of the vanadium redox flow battery (VII): Prediction of the viscosity of mixed electrolyte solution (VOSO4 + H2SO4 + H2O) based on Eyring’s theory

Viscosities of ternary mixtures of VOSO4 + H2SO4 with water were measured across the entire range of total ionic strength (IT = 1 to 11) mol·kg−1 and over a temperature range of (283.15–318.15) K. The viscosity B-coefficients of the binary aqueous were determined from Jones-Dole equation. Using the B-coefficients, the activation parameters for viscous flow of the solutes were further evaluated. On the basis of Eyring’s equation, a semi-empirical method to estimate the viscosity for concentrated and mixed electrolyte solutions was put forward. The estimated viscosity values of VOSO4 + H2SO4 + H2O are in quite good agreement with the corresponding experimental results with the average absolute relative deviation of 0.96%.

Physicochemical properties, 1H NMR, ab initio calculations and molecular interactions in a binary mixture of N-methylimidazole with ethyl acetate

For a binary mixture of x N-methylimidazole (hereafter abbreviated as N-mim) + (1 − x) ethyl acetate (hereafter abbreviated as EAC), the density, sound velocity, viscosity and refractive index at (288.15, 298.15, 308.15, 318.15, and 328.15) K, mixing enthalpy at 298.15 K, and 1H NMR measurements combined with the ab initio calculations were carried out over a full molar fraction range.The density, sound velocity, isentropic compressibility, refractive index, viscosity, Gibbs energy of activation of viscous flow and the isobaric thermal expansivity were correlated with a polynomial well. The excess molar volume, excess isobaric thermal expansivity, isobaric thermal expansivity deviation, excess sound velocity, sound velocity deviation, excess isentropic compressibility, isentropic compressibility deviation, excess refractive index, refractive index deviation, excess logarithm viscosity, viscosity deviation, excess Gibbs energy of activation of viscous flow and the molar mixing enthalpy, were calculated and fitted to a Redlich-Kister polynomial. The activation parameters of viscous flow of the mixture, chemical shift changes of N-mim and EAC protons, interaction energy and second-order perturbation stabilization energy of 2-CH···OC, 2-CH···N and CH···O H-bonds were calculated.The mixing process of N-mim with EAC is an endothermic process with volume contraction. The energy to break the like molecular interactions is bigger than that to form dislike molecular interactions, and the volume contraction is mainly attributed to both the free volume difference and the more effective steric accommodation of molecules in the mixture.The 2-CH···OC and 2-CH···N H-bonds are approximately equivalent in dimers, 2-CH···OC H-bond in dimer (N-mim + EAC) is stronger and more stable than the CH···O H-bonds in EAC dimer. The amount of 2-CH···OC H-bond reaches a zenith at x ≈ 0.5. The formation of 2-CH···OC H-bond leads to the electron density rearrangement of the N-mim and EAC molecules, where the electron densities of the N-mim and EAC protons decrease and increase, respectively.

Viscometric study of myo-inositol in aqueous deep eutectic solvent solutions

A viscometric study of myo-inositol in pure water and in Deep Eutectic Solvent (DES) aqueous solutions is presented. Two DES based on choline chloride as acceptor group and urea or glycerol as donor group are used. Experimental measurements of viscosities at p = 99.0 kPa and at six temperatures from 293.15 to 318.15 K were performed. In addition, the viscometric properties such as the B-coefficient, the hydration number, and the activation parameters of viscous flow were calculated. From these properties, the intermolecular interactions were evaluated. The results show that the studied sweetener is a structure-maker compound in all solvents of this work. The solute co-solute interactions are strongest in the system containing glycerol.

Structure of aqueous solutions of sucrose, derived from viscosimetry data and IR spectroscopy

The structural features of aqueous sucrose solutions are investigated via viscosimetry and IR spectroscopy in the 293.15–323.5 K range of temperatures at concentrations of 0–60%. Concentration dependences of the activation parameters of viscous flow, structural temperature, and energy and length of intermolecular hydrogen bonds are calculated based on the experimental data. It is shown that the solution became more structured with an increase in the sucrose concentration.

Volumetric, Acoustic and Transport Properties of Metformin Hydrochloride Drug in Aqueous d-Glucose Solutions at T = (298.15–318.15) K

Apparent molar volumes, apparent molar adiabatic compressibilities and viscosity B-coefficients for metformin hydrochloride in aqueous d-glucose solutions were determined from solution densities, sound velocities and viscosities measured at T = (298.15–318.15) K and at pressure p = 101 kPa as a function of the metformin hydrochloride concentrations. The standard partial molar volumes ( $$ \phi_{V}^{0} $$ ) and slopes ( $$ S_{V}^{*} $$ ) obtained from the Masson equation were interpreted in terms of solute–solvent and solute–solute interactions, respectively. Solution viscosities were analyzed using the Jones–Dole equation and the viscosity A and B coefficients discussed in terms of solute–solute and solute–solvent interactions, respectively. Adiabatic compressibility ( $$ \beta_{s} $$ ) and apparent molar adiabatic compressibility ( $$ \phi_{\kappa }^{{}} $$ ), limiting apparent molar adiabatic compressibility ( $$ \phi_{\kappa }^{0} $$ ) and experimental slopes ( $$ S_{\kappa }^{*} $$ ) were determined from sound velocity data. The standard volume of transfer ( $$ \Delta_{t} \phi_{V}^{0} $$ ), viscosity B-coefficients of transfer ( $$ \Delta_{t} B $$ ) and limiting apparent molar adiabatic compressibility of transfer ( $$ \Delta_{t} \phi_{\kappa }^{0} $$ ) of metformin hydrochloride from water to aqueous glucose solutions were derived to understand various interactions in the ternary solutions. The activation parameters of viscous flow for the studied solutions were calculated using transition state theory. Hepler’s coefficient $$ (d\phi /dT)_{p} $$ indicated the structure making ability of metformin hydrochloride in the ternary solutions.

Investigation of electrolytes of the vanadium redox flow battery (IV): Measurement and prediction of viscosity of aqueous VOSO4 solution at 283.15 to 323.15 K

Viscosity and density for aqueous VOSO4 solution have been measured in the concentration range of (0.05 to 0.3) mol·kg−1 at different temperatures from (283.15 to 323.15) K. On the basis of the measurements, the activation energy of viscous flow has been calculated by Arrhenius equation. A predicting function for the viscosity of aqueous VOSO4 has been proposed based on the viscosity coefficients A and B determined from Jones-Dole equation. In addition, the VO2+-water interaction and its effect on the structure of solvent according to the B-coefficient of VO2+ in dependence of temperature have been discussed. Using the B-coefficients, furthermore, the activation parameters for viscous flow of the solution, Δμ1≠0, Δμ2≠0, and other thermodynamics parameters ΔS2≠0, ΔH2≠0 and ΔCp2≠0 were evaluated. Finally, another empirical model of the viscosity has been investigated on the basis of the Eyring equation with the AAPD of 1.81%, and the maximum relative deviation is 2.77% below 313.15K, but up to 7.01% above 323.15K. Both predicting equations for the viscosities of aqueous VOSO4 are both in good agreement with the experimental results.

Interacciones moleculares de las soluciones acuosas diluidas de nitrato de sodio a partir de datos viscosimétricos

Se determinaron experimentalmente los tiempos de flujo de soluciones a NO3 + H2O en el intervalo de concentración molal 0,0000-0,9996 (mol/kg). Se usó un microviscosímetro automático Anton Paar®, modelo AMVn, a temperaturas desde 283,15 K hasta 318,15 K cada 5 K y presión atmosférica de 0,101 MPa. A partir de los datos obtenidos, se calcularon las viscosidades dinámicas (), los coeficientes de viscosidad, y de la ecuación de Jones-Dole, y los parámetros de activación del flujo viscoso (, y ) a dilución infinita. Los coeficientes resultaron positivos al igual que . De acuerdo con el análisis del signo de este último, el NaNO3 actúa como un soluto formador de la estructura del agua. Por otro lado, los parámetros de activación del flujo viscoso a dilución infinita (,y) revelaron que el proceso de flujo viscoso es endotérmico con un claro predominio de las interacciones ión-solvente.

Volumetric and viscometric behaviour of pyridoxine hydrochloride in aqueous tetrabutylammonium hydrogen sulphate solutions at different temperatures

Apparent molar volumes and viscosity B-coefficients for pyridoxine hydrochloride in aqueous tetrabutylammonium hydrogen sulphate (TBAHS) solutions were determined from solution density and viscosity measurements at T=(288.15–318.15)K and p=101kPa as a function of pyridoxine hydrochloride concentration. The standard partial molar volume and slopes, obtained from the Redlich-Meyer equation, have been interpreted in terms of solute-solvent and solute-solute interactions respectively. The viscosity data were analyzed using the Jones-Dole equation and the derived parameters A and B were interpreted in terms of solute-solute and solute-solvent interactions respectively. The standard volume of transfer and viscosity B-coefficients of transfer of pyridoxine hydrochloride from water to aqueous TBAHS solutions were derived to study various interactions in the ternary solutions. The activation parameters of viscous flow for the ternary solutions were also calculated and explained in terms of transition state theory.

Viscosity and activation parameters of viscous flow of L-arginine in aqueous D-maltose monohydrate system over the temperature range (298.15 to 308.15) K

Viscosity and activation parameters of viscous flow of L-arginine in aqueous D-maltose monohydrate system over the temperature range (298.15 to 308.15) K

Volumetric and transport properties of betaine hydrochloride drug in aqueous uracil solutions at T = (298.15–318.15) K

Apparent molar volumes and viscosity B-coefficients for betaine hydrochloride in aqueous uracil solutions were determined from solution densities and viscosities measured at T=(298.15–318.15)K and at pressure p=101kPa as a function of betaine hydrochloride concentrations. The standard partial molar volumes ϕV0 and slopes SV∗ obtained from Masson equation were interpreted in terms of solute–solvent and solute–solute interactions, respectively. Solution viscosities were analyzed using Jones–Dole equation and the viscosity A and B coefficients discussed in terms of solute–solute and solute–solvent interactions, respectively. The standard volume of transfer ΔtϕV0 and viscosity B-coefficients of transfer (ΔtB) of betaine hydrochloride from water to aqueous uracil solutions were derived to understand various interactions in the ternary solutions. The activation parameters of viscous flow for the studied solutions were discussed in terms of transition state theory. The structure making or breaking ability of betaine hydrochloride was discussed in terms of the sign of dϕE0/dTP.

Effect of paracetamol in aqueous sodium malonate solutions with reference to volumetric and viscometric measurements

Apparent molar volumes and viscosity B-coefficients for paracetamol in aqueous sodium malonate solutions were determined from solution densities and viscosities measured at T=(298.15 to 318.15)K and at pressure p=101kPa as a function of paracetamol concentrations. The standard partial molar volumes (ϕV0) and slopes (SV∗) obtained from Masson equation were interpreted in terms of (solute+solvent) and (solute+solute) interactions, respectively. Solution viscosities were analyzed using Jones–Dole equation and the viscosity A and B coefficients discussed in terms of (solute+solute) and (solute+solvent) interactions, respectively. The standard volume of transfer (ΔtϕV0) and viscosity B-coefficients of transfer (ΔtB) of paracetamol from water to aqueous sodium malonate solutions were derived to understand various interactions in the ternary solutions. The activation parameters of viscous flow for the studied solutions were discussed in terms of transition state theory. The structure making or breaking ability of Paracetamol was discussed in terms of the sign of (dϕE0/dT)P.