Excess Volume Of Mixing Research Articles

Hydrogen-bonded polymer blends: the influence of annealing on the interface composition of thin films

Blends of deuterated poly(methyl methacrylate) (d-PMMA) with poly(styrene-co-vinylphenol) (MPS), which contains 5, 10, or 15 mol % vinylphenol monomer units, and blends d-MPS (5%)/poly(butyl methacrylate) and d-MPS (5%)/PMMA are investigatee by neutron reflectivity. In the formation of blends, the excess volume of mixing was found to be negative for blends of MPS (5%) but positive for blends of MPS (10%) and MPS (15%). The volumes of all blends are decreased by anneling. The concentrations of MPS at both interfaces air/polymer and polymer/substrate tended to increase after annealing for all blends except the blend MPS (5%)/d-PMMA which showed a significant extent of composition changes

Polydioxolane in aqueous solutions. 1. Phase diagram

The phase diagram of a polydioxolane sample (M w =50 000) in aqueous solutions was constructed between -100 and +100°C in the whole range of composition. The solubility domain is limited at higher temperature by the demixing curve (lower critical solution temperature (LCST)= 70°C) and at lower temperature by the melting point of a hydrate (containing three water molecules per monomer unit), and this domain does not extend beyond a polymer content of 50% weightwise. The excess mixing volume is found to be negative and to go through a minimum at 45°C. These findings are compared to those of PEG in water

Thermodynamics of Binary Mixtures Containing Cyclic Ethers 1. Excess Volumes of Tetrahydrofuran + Chloroethanes or + Chloroethenes

Abstract Excess volumes of mixing, VE , for binary mixtures of tetrahydrofuran (THF) with 1,2-dichloroethane, 1,1,1-trichloroethane, 1,1,2,2-tetrachloroethane, trichloroethene and tetrachloroethene have been measured dilatometrically at 303.15 K over the entire composition range. Values of VE are negative in all the mixtures except in the system, THF + 1,2-dichloroethane, wherein an inversion in sign of VE is observed. The experimental results are interpreted in terms of molecular interactions.

Coordination variability and the structural components of silica glass under high pressures

The description of the structure of siliceous melts as the silicon ions transform from four- to six-fold coordination with increasing pressure is difficult because their structures range from open networks at low pressures to ones which are more nearly close-packed at pressures of 25–30 GPa. The effect of these coordination modifications on the density, diffusivity, viscosity and melting behavior of silicate liquids is of vital importance to the transport of partial melt in the mantle. Using molecular dynamics calculations, we have investigated the physical and structural characteristics of amorphous silica up to pressures of 135 GPa. The pairwise potential of S. Tsuneyuki and coworkers has previously been proven to be remarkably versatile in the simulation of several crystalline silica polymorphs. We point out some problems connected with its parameterization when used for amorphous phases at high pressures or high temperatures. We find large concentrations (30–50%) of five-fold coordinated Si atoms in square pyramidal geometry between 15 and 30 GPa. We describe some alternative interpretations of melt structure involving the Delaunay network and these are consistent with a model of liquid structure involving mixing of four-, five- and six-fold coordinated Si atoms with an associated negative excess mixing volume coupled with an ideal entropy of mixing on the order of 1–1.75 R. Neighbor cage backscattering effects are largely controlled by physical neighbor distances (those within the first radial distribution function coordination shell) and are not sensitive to the volume reduction of the surrounding Voronoi cell, but their behavior at long times may be controlled by the decreased Voronoi cell anisotropy at higher pressures.

Excess volumes of mixtures of alkanes with carbonyl compounds

Excess volumes of mixing were measured at 20 o C for mixtures of three linear alkanes (hexane, heptane, and octane) and cyclohexane with five alkyl acetates (methyl, ethyl, propyl, butyl, and amyl acetates) and two ketones (acetone and 2-butanone). The whole composition range was studied for all 28 binary systems. For a given alkane, the excess volume decreases with the increasing size of the carbonyl compound. For a given carbonyl compound, the excess volume increases with the size of the alkane

Excess volume of mixtures of selected alkyl esters and ketones with aromatic hydrocarbons

Excess volumes of mixing were measured at 20 C for mixtures of four aromatic hydrocarbons (benzene, toluene, ethylbenzene, and p-xylene) with five alkyl acetates (methyl, ethyl, propyl, butyl, and amyl acetates) and two ketones (acetone and 2-butanone). The whole composition range was studied for all 28 binary systems. Specific interactions between the carbonyl and aromatic systems lead to rather small excess volumes, frequently even negative ones. Ketones interact more strongly than alkyl acetates

Partial molal volumes of n-alkyl p-aminobenzoates in nonpolar solvents

The partial molal volumes of ethyl and n-butyl p-aminobenzoate were determined in seven solvents, including benzene, toluene, carbon tetrachloride, cyclohexane, n-dodecane, n-heptane and n-hexane. These p-aminobenzoates were found to have statistically larger partial molal volumes in the long-chain and cyclic alkanes than in the remaining five solvents. The higher partial molal volumes would contribute to deviations from ideal entropies of mixing in the form of excess volumes of mixing. Estimates of the solubility parameters for ethyl and n-butyl p-aminobenzoate were revised using the experimental partial molar volumes and solubility data for these two solutes in each of the seven solvents. The revised solubility parameters indicate that the experimental volumes do not reduce the previously reported variation in the solubility parameter when estimated from solubilities in these seven solvents. Consideration of the entropy of mixing in light of the experimental volumes showed no advantage over the assumption of an ideal entropy of mixing.

Excess volumes of mixing and excess enthalpies of mixing of n-butyl chloride with aromatic hydrocarbons at 298.15 K

The excess volumes and enthalpies of mixing of binary mixtures of n-butyl chloride with benzene, toluene, o-xylene, m-xylene and p-xylene have been measured experimentally over the whole composition range at 298.15 K. The data have been analysed qualitatively in terms of the specific interactions of electron donor-acceptor type and of the disruption of molecular order in the pure components. Flory's theory correctly predicts the sign and to an acceptable extent the magnitude of the H E values although the agreement for V E values is not good. However, the Graph theory correctly predicts the sign as well as the magnitude of the V E and H E values.

Volume‐Explicit Equation of State and Excess Volume of Mixing of Fused‐Hard‐Sphere Fluids

AbstractThe paper presents a simple analytic volume‐explicit equation of state (EOS) for fluids of hard bodies made up to fused hard spheres (FHS). Application of this EOS to both pure fluids and fluid mixtures (via Amagat's law) provides an accurate description of practically all existing computer simulation data. It is found that deviations from the assumption of ideal mixing are restricted essentially to low densities only; at higher densities small deviations are detected only for quite large volume ratio of molecules while the shape does not seem to play a significant role.

Density-composition data for eight binary systems containing toluene or ethylbenzene and C8-C16 n-alkanes at 293.15, 298.15, 308.15, and 313.15 K

Density-composition data for eight binary mixtures, viz., toluene-n-octane, toluene-n-decane, toluene-n-dodecane, toluene-n-tetradecane, toluene-n-hexadecane, ethylbenzene-n-octane, ethylbenzene-n-tetradecane, and ethylbenzene-n-hexadecane have been determined at 293.15, 298.15, 308.15, and 313.15 K over the entire composition range. The results have been correlated by polynomial expressions. The experimental data were also used to calculate excess volumes of mixing

Excess volume of mixing and excess enthalpies of mixing of ethyl iodide + aromatic hydrocarbons at 25�C

The excess volumes and enthalpies of mixing of binary mixtures of ethyl iodide with benzene, toluene, o-xylene, m-xylene and p-xylene have been measured experimentally over the whole composition range at 25°C. Qualitatively the data have been explained on the basis of electron donoracceptor interactions between the ethyl iodide and aromatic hydrocarbons and also on the loss of favorable orientational order of the pure components. Flory's theory correctly predicts the sign and to some extent magnitude of the VE and HE values.

The thermodynamics of solutions of polyperfluoropylene oxide in perfluorinated and other solvents

Apart from its intrinsically valuable physical properties in industrial applications polyperfluropropylene oxide (PPFPO), usually marketed as Fomblin Fluids of varying grades, is a valuable model substance for the study of the solution behavioral of a perfluorinated polymer . This is particularly so given the characteristic insolubility in any solvent of polyperfluoroethylene, the only the perfluorinated polymer.We report here the solution properties of PPFPO in a variety of solvents ranging from hexafluoroethane to tri-nonafluorobutymine. The properties studied are the excess volumes of mixing and the orthobaric lower critical loci as a function of temperature, pressure, composition, and polymer and solvent chain lengths.The phase behaviour is discussed in terms of the Prigogine corresponding states theory. A requirement of the application of this theory is a knowledge of the degree of conformity of the solvents to a principle of corresponding states. Both the results needed to carry out this test and the outcome of the analysis are reported.

Studies on the excess volume of mixing in blends of poly(methyl methacrylate) and poly(vinylidene fluoride)

The excess volume of mixing ΔV m of blends of poly(methyl methacrylate) (PMMA) and poly(vinylidene fluoride) (PVDF) was determined by dilatometry. This quantity turned out to be positive for all concentrations, in contradiction to expectations based on the equation-of-state theory. Computer simulations were performed within the framework of this theory to obtain conditions in terms of the equation-of-state variables p∗ and T∗, for which the excess volume of mixing is predicted to be positive. The corresponding values are well beyond the range of those characteristic for PVDF and PMMA. The conclusion is that structural changes induced by strong interactions between the components may be the origin of positive values of ΔV m.

Excess volumes of mixing and excess enthalpies of mixing of 1,2-dibromoethane with aromatic hydrocarbons at 298.15 K

The excess volumes and enthalpies of mixing of binary mixtures of 1,2-dibromoethane with benzene, toluene, o-xylene, m-xylene and p-xylene have been measured experimentally over the whole composition range at 298.15 K. Qualitatively, the data have been explained on the basis of electron donor/acceptor interactions between 1,2-dibromoethane and the aromatic hydrocarbons and also on the basis of the loss of favourable orientational order of the pure components. The Flory theory is not able to correctly predict the V E and H E values of the studied systems. However, the Sanchez and Lacombe theory correctly predicts the change of sign of the H E values with change of mole fraction. H E calculated by this theory is of the same order as the experimental H E The calculated values for V E are in poor agreement with the corresponding experimental values for V E.

Mixtures of 1-1 electrolytes: Densities and excess volumes of aqueous NaCl-NaBr solutions at 25�C

The relative densities and excess volumes of mixing are reported for the system consisting of aqueous NaCl and NaBr at 25°C at constant ionic strengths of 0.5, 1, 2, 3, and 4 mol kg−1 of water. The measurements of densities are precise to 3 · 10−6 g cm−3. The densities, apparent molal volumes and excess volumes are analysed with the virial coefficients approach with excellent accuracy. The excess volumes are positive throughout.

Ion mobilities in DMF-water mixtures at 25�C

Densities and viscosities of mixtures of N,N-dimethylformamide (DMF) with water at 25°C have been determined. Limiting equivalent conductances of cesium chloride, potassium chloride, potassium bromide and potassium thiocyanate in these solvent mixtures at 25°C are presented together with corresponding values of ion association constants and distance of closest approach parameters. The transference number of the potassium ion has been determined in solvent mixtures ranging from 0 to 0.75 mol fraction in DMF in water at 25°C. The conductimetric Hittorf method has been used for both potassium bromide and potassium chloride in solutions of up to 0.496 mole fraction of DMF. For solutions of potassium thiocyanate in 0.5 and 0.75 mole fraction in DMF the cationic transference number has been determined using the moving boundary method. Stokes radii have been evaluated. Transport properties are examined in relation to-solvent properties such as composition, dielectric constant, excess volume of mixing and free volume.

Piezothermal investigation of a phase equilibrium at high pressure: the acetone-carbon disulfide mixture

The piezothermal behavior of a two-component mixture has been investigated for the first time. Acetone-CS 2 mixture have been examined as a function of pressure and temperature at different compositions. Far from the critical regions each mixture exhibits all the features of a pure liquid. The excess volume of mixing has been determined in this case, as a function of the three variables p, T, and x, with respect to a known reference in the plane (p,x)

Excess molar volumes, speeds of sound, and isentropic compressibilities of binary mixtures of furfural with some aromatic hydrocarbons

Molar excess volumes of mixing and isentropic compressibilities for the binary mixtures of furfural with benzene, toluene, ethylbenzene, and o-, m-, and p-xylenes at 308.15 K have been measured. The results reveal that geometric factors are predominant in determining the solution behaviour of the binary mixtures under investigation.

Energetics of brannerite-type solid solutions: The systems ZnV 2O 6LiMoVO 6 and MgV 2O 6LiMoVO 6

Enthalpies of mixing in brannerite-type solid solutions ZnV 2O 6LiMoVO 6 and MgV 2O 6LiMoVO 6 were determined by transposed temperature-drop solution calorimetry into a molten sodium molybdate solvent at 702°C. The ZnV 2O 6LiMoVO 6 system shows zero heats of mixing (to ± 2 kJ/mole) and symmetrical negative excess volumes of mixing. The MgV 2O 6LiMoVO 6 system shows more complex behavior, with positive enthalpies of mixing at MgV 2O 6-rich end and negative heats of mixing at LiMoVO 6-rich compositions. Volumes of mixing are negative at MgV 2O 6-rich compositions and essentially zero on the LiMoVO 6-rich side. This complex behavior suggests that several effects compete to result in the observed energetic and structural behavior. These factors may be (a) strain energy associated with size-mismatch, (b) the relaxation of rather long MgO bonds in MgV 2O 6 upon solid solution formation, and (c) the effect of simultaneous coupled substitution of Li on Mg sites and of Mo on V sites, possibly with some short-range order.

Heats of dilution of water-soluble polymer solutions

In order to obtain information about the effects of water on water-soluble polymers, the heats of dilution of poly(acrylic acid)-water and poly(acrylic acid)-ethyl alcohol systems were measured at 298.15 ± 0.002 K with a specially constructed automatic microcalorimeter. The results obtained show that the heat of dilution is endothermic for the water system and exothermic for the ethyl alcohol system. In order to confirm the endothermic and/or exothermic heats of dilution of those systems, the excess volume of mixing of the systems was also measured at 298.15 ± 0.01 K using a densimeter. The sign of the excess volume for the ethyl alcohol system, but not for the water system, was in good agreement with that of the interaction heat parameter estimated by calorimetry. To obtain further information about the interaction, the interaction energies of the systems were calculated by means of ab initio molecular orbital (MO) calculations. The result obtained is about −12 kJ mol −1 for the ethyl alcohol system, suggesting that the interaction mode between poly(acrylic acid) and ethyl alcohol molecules may be based on the hydrogen bond between the COOH group in the chain of poly(acrylic acid) and the OH in the ethyl alcohol molecule from the agreement of the heats of dilution with the excess volume of mixing and/or ab initio MO calculations. However, for the water system, the interaction energy obtained is positive and its value is very large.