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

Abstract

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.

Determination of solvent/polymer interaction parameters of moderately concentrated polymer solutions by vapor pressure osmometry

“…Data of investigation are summarized in Tables 3 (FH model) The interaction parameter, c 23 , for PSU is constant in the investigated concentration range, but not for PES. The temperature dependency can be neglected, which is also in accordance with Barth and Wolf [7]. Data evaluation using the FH model results in higher parameter values for c 23 compared to the virial expansion.…”

“…3 displays, as an example, the experimental equilibrium vapor pressure of DMF as a function of the volume fraction of PSU, in both the semi-diluted and the concentrated regimes. Data in the semi-diluted regime were obtained in this work while for the concentrated regime experiments of Barth and Wolf [7] were used.…”

“…However, for the typical concentration range of membrane formation (polymer concentration between about 10 and 30 wt.%) only very few suitable c 23 data (not to mention their concentration dependencies) can be found. Recently, Barth and Wolf [7] introduced headspace gas chromatography as a method to measure partial pressures of volatile components (solvents) in different homogeneous binary systems. However, precise measurements require concentrations higher than 25 wt.%.…”

Influences of different preparation variables on polymeric membrane formation via nonsolvent induced phase separation

“…Nonsolvent induced phase separation (NIPS) is one of the most frequently applied approaches for PES membrane fabrication . It enables the production of asymmetric structures with a large range of different characteristics, since the resulting membrane properties can be largely controlled if the formation process is well understood . During NIPS a homogenous PES solution is immersed into a nonsolvent bath .…”

Role of thermodynamic and kinetic interaction of poly(vinylidene fluoride) with various solvents for tuning phase inversion membranes

“…Experimental and theoretical studies of thermodynamics based on Flory-Huggins theory have been undertaken extensively for cellulose acetate and its derivatives [1][2][3][4], polysulfone [5,6], polyethersulfone [5][6][7][8], and polyacrylonitrile [9]. Data derived from thermodynamic model are used to predict the kinetic pathway during phase inversion [9].…”