Surface-initiated atom transfer radical polymerization: A new method for preparation of polymeric membrane adsorbers

This contribution demonstrates a method for preparing high-capacity membrane adsorbers by growing surface-tethered, charged polymer nanolayers from the surfaces of regenerated cellulose (RC) membranes (average pore diameter 1 μm). Surface-initiated atom transfer radical polymerization was used to grow the cation-exchanger poly(acrylic acid) (PAA). By varying the polymerization time, the thickness of the nanolayer was controlled. Characterization was done by ATR-FTIR spectroscopy to follow the modification steps. Water flux measurements illustrated that polymerization time could be used to decrease average effective pore sizes controllably. Pore-size distributions measured by liquid dewetting permporometry also confirmed that polymer chains were grown from the surface of the membrane pores. Static and dynamic binding capacities were measured for lysozyme on the PAA-modified RC membranes. Capacities initially increase with increasing modification times and reach maximum values of 98.5 mg/ml (static) and 71.2 mg/ml (dynamic). Confocal laser scanning microscopy (CLSM) was used to visualize binding of fluorescently labeled lysozyme on the unmodified and PAA-modified membranes. CLSM of labeled membranes also showed that the modification procedure had no detrimental effects on the membrane pore structure.