PHOTOMODIFICATION OF ULTRAFILTRATION MEMBRANES .2. ULTRAFILTRATION PROPERTIES OF POLYACRYLONITRILE MEMBRANES PHOTOCHEMICALLY MODIFIED WITH ARYL AZIDES

The aim of the studies was to characterize the ultrafiltration properties of a variety of photochemically modified membranes, made by a new approach starting with two types of PAN-UF membranes and using nine aromatic azides bearing different more or less hydrophilic or hydrophobic substituents. The influence of the surface functionalization (hydrophilization, 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 solutions of ovalbumine and lysozyme was the major subject. Modified membranes made using the aryl azides with hydrophilic groups, 4-azidobenzoic 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 permeability, enhanced dextrane selectivity, and significant flux reductions as a consequence of contact with ovalbumin solutions (pH = 5.0). The strongest effects were achieved with the two expecially hydrophobic compounds, 2-naphthyl azide, Ih, and 2-naphthoyl azide, IX. On the other hand, a pronounced positive effect of photo-modification on the protein fouling behaviour became evident in the UF of lysozyme (0.05%, pH = 10.5). Using the membranes modified with Id a much higher filtrate flux (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.