Asymmetric polysulfone and polyethersulfone membranes: effects of thermodynamic conditions during formation on their performance

Membranes of polysulfone (PSU) and polyethersulfone (PES) were prepared fro m ternary and quaternary mixtures containing N,N-dimethylformamide (DMF) as solvent, water as non-solvent, and acetone (AC) as additive. The condition s for phase inversion and the desired phase separation mechanisms were sele cted on the basis of the phase behavior determined for the solvent/non-solv ent/polymer systems. The influences of the composition of the casting solut ion, of the support, and of film thickness on structure and permeation prop erties of the membranes were analyzed by scanning electron microscopy (SEM) plus flux and separation experiments. The mechanisms of phase inversion th at should prevail under the different conditions according to the measured phase diagrams were corroborated by means of light scattering experiments. (C) 2000 Elsevier Science B.V. All rights reserved.