Modification of polysulfone membranes 3. Effect of nitrogen plasma

The paper considers properties of porous membranes modified by action of ni trogen plasma. The membrane material was polysulfone - the polymer most fre quently used in production of ultrafiltration membranes. It is shown that 2 .45 GHz nitrogen plasma generates various kinds of surface functionalities both of acidic and basic character. The surface changes during the first we ek after plasma treatment, some groups disappear some others are shifted to wards surface. In consequence, surface hydrophilicity gained during plasma treatment decreases but does not disappears completely. It is shown that mo dified ultrafiltration membranes are less prone to protein fouling than the ir untreated analogues. This protection is extended on a wide range of rete ntate pH-values. Plasma action alters also morphology of membranes. During first 2 min of action, polymer ablation seems to dominate. Pore diameter be comes larger and pores size distribution wider. Longer exposition to plasma does not affect pores any more - the rates of ablation and deposition seem to be balanced. (C) 2000 Elsevier Science Ltd. All rights reserved.