Antifouling Oligoethylene Glycol-Functionalized Aromatic Polyamides Brushes Synthesized via Surface-Initiated Chain-Growth Condensation Polymerization

With growing freshwater scarcity in many areas of the world, purifying alternative sources of water such as seawater, brackish water, and wastewater has become increasingly important. One of the main ways this is done is using reverse osmosis (RO) membranes composed of aromatic polyamide films synthesized using interfacial polymerization. These membranes have become the industry standard due to their excellent salt rejection. However, issues with fouling, degradation, and delamination plague current technology, which has led to renewed interest in finding innovative solutions. Polyethylene glycol (PEG) has been used extensively for its antifouling properties and has been incorporated into RO membranes with some success. In this study, oligoethylene glycol (OEG)-functionalized aromatic polyamides were covalently grown using surface initiation from silicon wafers, quartz crystal microbalance (QCM) sensors, and silica particles to form high grafting density polymer brushes. Initially, solution-based kinetic studies were used to optimize the polymerization conditions of the OEG-functionalized monomers. The optimized conditions were then used for surface-initiated substituent effect chain-growth condensation polymerization of the monomers. The use of these conditions produced uniform OEG-functionalized aromatic polyamide brushes with well-defined molecular weight and narrow molecular weight distribution. QCM and atomic force microscopy were used to demonstrate the drastically improved antifouling characteristics of the brushes as compared to PEG monolayers and aromatic polyamides brushes without the OEG functionalization.