Surface modification of poly(ether sulfone) ultrafiltration membranes by low-temperature plasma-induced graft polymerization

Low-temperature helium plasma treatment followed by grafting of N-vinyl-2-p yrrolidone (NVP) onto poly(ether sulfone) (PES) ultrafiltration (UF) membra nes was used to modify commercial PES membranes. Helium plasma treatment al one and post-NVP grafting substantially increased the surface hydrophilicit y compared with the unmodified virgin PES membranes. The degree of modifica tion was adjusted by plasma treatment time and polymerization conditions (t emperature, NVP concentration, and graft density). The NVP-grafted PES surf aces were characterized by Fourier transform infrared attenuated total refl ection spectroscopy and electron spectroscopy for chemical analysis. Plasma treatment roughened the membrane as measured by atomic-force microscopy, A lso, using a filtration protocol to simulate protein fouling and cleaning p otential, the surface modified membranes were notably less susceptible to B SA fouling than the virgin PES membrane or a commercial low-protein binding PES membrane. In addition, the modified membranes were easier to clean and required little caustic to recover permeation flux. The absolute and relat ive permeation flux values were quite similar for the plasma-treated and NV P-grafted membranes and notably higher than the virgin membrane. The main d ifference being the expected long-term instability of the plasma treated as compared with the NVP-grafted membranes. These results provide a foundatio n for using low-temperature plasma-induced grafting on PES with a variety o f other molecules, including other hydrophilic monomers besides NVP, charge d or hydrophobic molecules, binding domains, and biologically active molecu les such as enzymes and ribozymes. (C) 1999 John Wiley & Sons, Inc.