(386e) Dual-Functional Nanofiltration Membranes Exhibit Multifaceted Ion Rejection and Antifouling Performance

The incorporation of charged functional groups is often used to facilitate the selective rejection of multivalent ions over monovalent ions by nanofiltration (NF) membranes. However, the incorporation of charged functionality can accelerate membrane fouling. Multifunctional membrane architectures that incorporate distinct layers of chemical functionality over their cross section provide a strategy for balancing the competing demands associated with making NF membranes that are both fouling-resistant and ion rejecting. Here, poly(trifluoroethyl methacrylate-co-oligo-(ethylene glycol) methyl ether methacrylate-co-(3-azido-2-hydroxypropyl methacrylate)) copolymer parent substrates, which can be modified using the copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) reaction, were exposed to a series of reactive solutions containing alkyne-terminated molecules to create dual-functional membranes. Using appropriately controlled exposure conditions, the CuAAC reaction propagates into the copolymer substrate as a reactive front. This phenomenon allows for the creation of layered domains of distinct anti-fouling zwitterionic and ion rejecting sulfonate functionality. The ion rejection and fouling propensity for a family of dual-functional membranes was examined. For membranes with a thin anti-fouling layer on top of an ion rejection layer, the rejection of 1 mM K₂SO₄, 87%, was comparable to the value for full charge control membranes, 90%. Moreover, when exposed to a fouling solution containing bovine serum albumin (BSA), these dual-functional membranes exhibited an 18% decline in normalized flux and recovered 99% of their flux upon rinsing. Comparatively, the full charge membranes exhibited a 44% decline in normalized flux and recovered 65% of their flux upon washing. As such, the results demonstrate that the controlled functionalization process reported here is capable of balancing anti-fouling and ion rejection capabilities. Furthermore, the versatile nature of the click chemistry mechanism at the center of this process offers a means by which to design and fabricate multifunctional membranes for numerous future applications.