Postfunctionalization of PAN Membranes via UV-Grafting of Charged and Zwitterionic Polymer Brushes

Polyacrylonitrile (PAN) membranes are widely used for water purification, but their susceptibility to fouling limits efficiency and lifespan. In this study, a sustainable and efficient UV-grafting process was employed to modify PAN membranes. Cationic and zwitterionic vinylbenzene- and methacrylate-based monomers, including ammonium, ammonium alcohol, N-oxide, carboxybetaine, sulfobetaine, and phosphobetaine groups, were used to graft polymers from the membrane surface using photoinitiators such as phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide (BAPO) and lithium phenyl-2,4,6-trimethylbenzoylphosphinate (LAP). The modified membranes were characterized using FTIR, SEM-EDX, AFM, ζ potential analysis, permeability testing, molecular weight cutoff measurements, dye adsorption assays, porosity, and pore size analysis. Microbiological evaluation following a modified ASTM E2149-20 protocol revealed antibacterial properties for some of the grafted polymers. These findings demonstrate the potential of postfunctionalized PAN membranes for the adsorption of dyes and to mitigate fouling, both are important factors for water treatment.