Vitrification phenomena in polysulfone/NMP/water system

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 α- and β-transition temperatures (Tg,α = 187.5°C, Tg,β = −21.4°C). The Tg,α of PSf decreased with increasing solvent concentration. The Tg,α 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.