EQUILIBRIUM THERMODYNAMICS OF A QUATERNARY MEMBRANE-FORMING SYSTEM WITH 2 POLYMERS .2. EXPERIMENTS

Concentration-dependent binary Flory-Huggins interaction Parameters be longing to the quaternary system poly(ether sulfone) (PES)-poly(vinylp yrrolidone) (PVP)-N-methylpyrrolidone (NMP)-water are determined by me ans of high-pressure osmometry. The interaction parameter between PVP and water was in accordance with literature values. The interaction pa rameters between PES and NMP and between PVP and NMP were found to be slightly concentration dependent; the values indicate near-THETA condi tions for both polymers in the solvent. The binary interaction paramet er between the polymers PES and PVP is estimated from ternary osmotic measurements and found to be quite low: between -0.5 and -1.0. This is in accordance with earlier findings. Cloud point curves were evaluate d experimentally and theoretically.1 The agreement between theory and experiment was qualitative.