PHOTOMODIFICATION OF ULTRAFILTRATION MEMB RANES .2. ULTRAFILTRATION PROPERTIES OF POLYACRYLONITRILE MEMBRANES PHOTOCHEMICALLY MODIFIED WITHARYL AZIDES

The aim of the studies was to characterize the ultrafiltration propert ies of a variety of photochemically modified membranes, made by a new approach starting with two types of PAN-UF membranes and using nine ar omatic azides bearing different more or less hydrophilic or hydrophobi c substituents. The influence of the surface functionalization (hydrop hilization, introduction of charges/hydrophobization) realized by this means onto the water permeability, the dextrane selectivity, and the permeabilities during and after UF, resp., after simple contact with s olutions of ovalbumine and lysozyme was the major subject. Modified me mbranes made using the aryl azides with hydrophilic groups, 4-azidoben zoic acid, lb, (4-azidophenyl)trimethylammonium iodide, If, sodium (4- azido)-benzene sulfonate, Id, showed enhanced water fluxes and reduced dextrane retention. All the other azides caused reduced water permeab ility, enhanced dextrane selectivity, and significant flux reductions as a consequence of contact with ovalbumin solutions (pH = 5.0). The s trongest effects were achieved with the two expecially hydrophobic com pounds, 2-naphthyl azide, Ih, and 2-naphthoyl azide, IX. On the other hand, a pronounced positive effect of photo-modification on the protei n fouling behaviour became evident in the UF of lysozyme (0.05%, pH = 10.5). Using the membranes modified with Id a much higher filtrate flu x (J(v) = 48.1 l/m2 h) was observed as compared with the original PAN membrane (J(v) = 13.1 l/m2 h). The perspectives and the limitations of the developed modification strategy are discussed.