ABSTRACT:The cloud point curves for polysulfone (PSf)/solvent/water systems were determined by a titration method. A small amount of water was needed to induce liquid-liquid demixing and the temperature effect was small. From numerical calculations, it was found that the binary interaction parameters for the PSf/solvent/water system enlarges the homogeneous region in the phase diagram with a smaller nonsolvent-polymer interaction parameter x 13 , a greater nonsolvent-solvent interaction parameter x 12 , and a smaller solvent-polymer interaction parameter x 23 and the effect of polymer molecular weight was negligible except in the range of low molecular weight. The phase diagrams, calculated with constant x 12 that was chosen from the concentration-dependent interaction parameter g 12 value of the concentration range, were similar to the results obtained with g 12 . The slope of the tie lines indicated that demixing of the ternary system occurred at relatively similar nonsolvent concentration in both phases. A value of 2.7 for the water-PSf interaction parameter was obtained by fitting the experimental cloud point curve with the calculated binodal lines.

ABSTRACT:The vitrification line for the ternary system of polysulfone (PSf)/N-methyl-2-pyrrolidinone (NMP)/water was determined by differential scanning calorimeter (DSC) measurements with varying compositions. Pure PSf showed both ␣-and ␤-transition temperatures (T g,␣ ϭ 187.5°C, T g,␤ ϭ Ϫ21.4°C). The T g,␣ of PSf decreased with increasing solvent concentration. The T g,␣ of PSf decreased linearly with the addition of NMP in the concentration range of 70 -90 wt % polymer. The vitrification line was indicated in the phase diagram for the ternary system of PSf/NMP/water at 15 and 60°C. As the temperature is increased, a high polymer concentration was needed to reach the vitrification condition. The vitrification composition of the polymer in the binary system of PSf and NMP was 72.0 wt % at 15°C and 79.8 wt % at 60°C. We also found that the slope of the vitrification line changed with the temperature and that a small amount of water (10 -20 wt %) can induce the vitrification of the polymer solution in the PSf/NMP/water system at 15°C.

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To construct a phase diagram of the polysulfone (PSF)/polyethersulfone (PES)/N-methyl-2-pyrrolidone (NMP)/water quaternary system, cloud point measurements were carried out by a titration method. The miscible region in the PSF/PES/ NMP/water quaternary system was narrow compared to the PSF/NMP/water and PES/NMP/water ternary systems. The binary interaction parameters between PSF and PES were estimated by water sorption experiments. The calculated phase diagram based on the Flory-Huggins theory fit the experimental cloud points well. In addition to the usual polymer-liquid phase separation, polymer-polymer phase separation, which resulted in a PSF-rich phase and a PES-rich phase, was observed with the addition of a small amount of nonsolvent. The boundary separating these two modes of phase separation could be well described and predicted from the calculated phase diagrams with the estimated binary interaction parameters of the components.