(Vapour + liquid) equilibria of (water + dimethylformamide): application of the headspace-gas chromatography for the determination of thermodynamic interactions

Barth, Cláudia; Horst, Roland; Wolf, B. A.

doi:10.1006/jcht.1997.0333

Cited by 21 publications

(17 citation statements)

References 1 publication

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“…The signals are sent to an integrator (Shimadzu Chromatopac C-R6A) which calculates the peak areas being proportional to the amount of gas in the sample volume and consequently to the vapor pressure. A more detailed description of the machine and the method can be found in the literature 4,8) .…”

Section: Methodsmentioning

confidence: 99%

“…The determination of the Flory-Huggins interaction parameter for DMF/H 2 O via the HSGC, its discussion and comparison with literature data was already reported elsewhere 4) . These investigations have shown that g DMFaH 2 O can be described best with the equation of Koningsveld and Kleintjens 6) (Eq.…”

Section: The Subsystem Dmf/watermentioning

confidence: 99%

“…From the partial pressures, measured for different compositions of the binary mixtures, the interaction parameters g ij (u i ) are calculated by minimizing the Helmholtz energy of mixing (the reasons and consequences of the use of the Helmholtz energy instead of the Gibbs energy have already been discussed 3,4) ). This procedure uses two combined iteration processes.…”

Section: Theorymentioning

confidence: 99%

“…The evaluation of the vapor pressure data for the homogeneous binary subsystems solvent/non-solvent and solvent/polymer, determined with the HSGC method, can be performed in a similar way 3,4) . According to Eq.…”

Section: Theorymentioning

confidence: 99%

See 3 more Smart Citations

Quick and reliable routes to phase diagrams for polyethersulfone and polysulfone membrane formation

Barth

Wolf²

2000

Macromol. Chem. Phys.

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Phase diagrams were measured and calculated for the ternary membrane forming systems DMF/water/polysulfone and DMF/water/polyethersulfone at different temperatures. Customary experiments yielded cloud point curves, tie lines, and critical compositions. The theoretical computation starts from the Flory‐Huggins theory and employs binary interaction parameters gij that vary with the composition. This information was mainly obtained by means of Headspace‐Gas Chromatography (HSGC, yielding the partial pressures of the volatile components); these data were complemented by light scattering and swelling experiments. The calculation of binodals, spinodals, tie lines, and critical points avoids the elaborate use of chemical potentials and minimizes the Gibbs energy directly. In order to reach total agreement between measured and calculated ternary phase diagrams it is necessary to adjust the interaction parameter between the polymers and water. Discrepancies between the values obtained in this way and the values resulting from measurements with the binary subsystems indicate the necessity of ternary interaction parameters gijk.

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Section: Methodsmentioning

confidence: 99%

Section: The Subsystem Dmf/watermentioning

confidence: 99%

Section: Theorymentioning

confidence: 99%

Section: Theorymentioning

confidence: 99%

See 2 more Smart Citations

Quick and reliable routes to phase diagrams for polyethersulfone and polysulfone membrane formation

Barth

Wolf²

2000

Macromol. Chem. Phys.

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“…From these data it is possible to calculate partial pressures of the volatiles. A detailed description of machine and method has already been reported 5,6,8) . Measurements were performed within the homogeneous region of the ternary systems, which has already been known from previous experiments 7) , keeping the composition of the mixed solvent constant.…”

Section: Headspace Gas Chromatographymentioning

confidence: 99%

Preferential evaporation of precipitants from polymer solutions in mixed solvents

Barth

Wolf

2000

Macromol. Rapid Commun.

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Enthalpy and Entropy Contributions to Solvent Quality and Inversions of Heat Effects with Polymer Concentration

Bercea

Wolf

2006

Macro Chemistry & Physics

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Summary: Vapor pressures above the solutions of polystyrene in either cyclohexane (32–60 °C) or toluene (10–70 °C) have been measured by a combination of head space sampling and gas chromatography as a function of the volume fraction φ of the polymer. The thus obtained Flory‐Huggins interaction parameters χ (φ; T) were complemented by data for three other systems (tert‐butyl acetate/polystyrene, cyclohexane/poly(vinyl methyl ether), 2‐propanol/poly(butyl methacrylate)) reported in the literature and analyzed in terms of their enthalpy and entropy parts χH and χS. Furthermore these experimental findings were modeled by means of an approach splitting the mixing process conceptually into two parts and leading to the expression χ = χfc + χcr. The first step takes place at fixed conformation of the components and yields χfc; equilibrium is reached in the second step, during the conformational relaxation, contributing χcr. The results demonstrate that mixing can either be driven enthalpically or entropically. By contrast the conformational response acts in all cases towards homogeneous mixing. The inversion of heat effects observed for two of the five systems can be well modeled in terms of the composition dependence of the enthalpy parts of χfc and χcr.Composition dependence of the enthalpy part, χH, of the Flory‐Huggins interaction parameter, and of the heat effects associated with the dilution in two steps.magnified imageComposition dependence of the enthalpy part, χH, of the Flory‐Huggins interaction parameter, and of the heat effects associated with the dilution in two steps.

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(Vapour + liquid) equilibria of (water + dimethylformamide): application of the headspace-gas chromatography for the determination of thermodynamic interactions

Cited by 21 publications

References 1 publication

Quick and reliable routes to phase diagrams for polyethersulfone and polysulfone membrane formation

Quick and reliable routes to phase diagrams for polyethersulfone and polysulfone membrane formation

Preferential evaporation of precipitants from polymer solutions in mixed solvents

Enthalpy and Entropy Contributions to Solvent Quality and Inversions of Heat Effects with Polymer Concentration

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