Controlling biofouling of reverse osmosis membranes through surface modification via grafting patterned polymer brushes

Thin film composite (TFC) polyamide membranes are extensively used as selective barriers in reverse osmosis processes. The major challenge faced with TFC membranes is significant fouling on the surface, which restricts the overall purification performance. To address the fouling problem, we developed novel fouling-resistant surface coatings via polyelectrolyte [poly(allylamine hydrochloride)/poly(styrene sulfonate)] layer-by-layer self-assembly, functionalized with patterned antimicrobial and antifouling/fouling-release polymer brushes. Two types of different polymer brushes, among antimicrobial poly(quaternary ammonium), antifouling poly(sulfobetaine) and fouling-release poly(dimethylsiloxane) (PDMS), were selected and grafted in a checkerboard pattern, with a square feature of 2 µm. The successful patterning and incorporation of different polymer brushes on the membrane was confirmed through X-ray photoelectron spectroscopy analysis. Grafting with sulfobetaine and PDMS significantly increased the hydrophilicity and lowered the surface energy of the membrane, respectively. The fouling-resistant property of the modified membrane was evaluated via static protein (bovine serum albumin) deposition and bacterial (Escherichia coli) cell adhesion tests. Surface modifications proved to diminish protein adhesion and exhibited 70–93% reduction in bacterial cell attachment. This observation suggests that the modified membranes have strong antifouling properties that inhibit the irreversible adhesion of organic and bio-foulants on the membrane surface.