Scalable Zwitterionic Polymer Brushes for Antifouling Membranes via Cu⁰-Mediated Atom Transfer Radical Polymerization

Polymer brush layers have attracted significant interest for versatile, controlled surface modification enabling fabrication and functionalization of membranes for water treatment and reuse applications. In particular, zwitterionic polymer brushes have been shown to provide strong resistance to organic fouling, oil fouling, biofouling, and inorganic fouling as membrane coatings for a variety of membrane processes. However, despite the demonstrated performance of polymer brush membranes, there are significant challenges associated with commercial scale-up of traditional fabrication methods. In this work, we demonstrate scalable grafting of zwitterionic polymer brushes from microfiltration membrane substrates under ambient conditions, and with low chemical consumption, for the first time, via Cu⁰-mediated surface-initiated atom transfer radical polymerization (Cu⁰-SI-ATRP). We demonstrate that Cu⁰-SI-ATRP is effective for brush grafting from porous membrane substrates, including samples of up to 150 cm². Furthermore, we systematically investigate the effect of polymerization in confinement on brush growth kinetics and fouling resistance, using colloid probe force microscopy and dynamic fouling experiments. Results demonstrate that Cu⁰-SI-ATRP results in poly(sulfobetaine methacrylate) brush layers that significantly improve fouling resistance; however, polymerization methods significantly impact fouling resistance, for both Si wafer and membrane substrates. We identify polymerization methods that enhance fouling resistance even for thin brush layers. The results of this study provide pathways to the scalable fabrication and design of robust, antifouling membranes for applications in water treatment, water reuse, and resource recovery from waste streams.