The need for nanofiltration (NF) membranes with tailored selectivity and reduced fouling propensity has led to the development of a multitude of processes that incorporate targeted functionality on membrane surfaces. Using copolymer materials, which form uniform nanoscale pores that are decorated with tunable chemical moieties, provides a ready means for post-assembly functionalization. For example, the incorporation of charged functionalities increases ion rejection by NF membranes due to repulsive electrostatic interactions. However, the incorporation of charge functionality tends to exacerbate the process of fouling, which is a continued hurdle in the development and application of membranes. Fouling is the process whereby attractive interactions between dissolved solutes and the membrane leads to accumulation of material on the membrane, reducing throughput. Introducing the desired charged and antifouling functionalities on a time scale consistent with modern roll-to-roll manufacturing is a central challenge in membrane functionalization. This study analyzes the incorporation of multiple functionalities onto a single membrane template. Membranes were cast from a poly(trifluoroethyl methacryltate-co-oligo-(ethylene glycol) methyl ether methacrylate-co-(3-azido-2-hydroxypropyl methacrylate)) P(TFEMA-OEGMA-AHPMA) copolymer. The copper-catalyzed azide-alkyne cycloaddition (CuAAC) click reaction offers a viable post-fabrication functionalization process, reacting with the azido groups lining the pore wall. The rate of membrane functionalization was controlled through the formulation of the reactive solution, with an initial propiolic acid solution followed by a propargylamine solution, each offering reaction pathways for the addition of antifouling, zwitterionic and ion rejecting sulfonate functionalities, respectively. Rapid exposure to the initial solution results in a controlled penetration depth, in which distinct functionalities were incorporated at fixed distances across the membrane thickness. Optimizing the thickness of the antifouling layer results in dual-functionalized membranes that exhibit similar rejections of MgCl2 and K2SO4 compared to a fully charged membrane, while increasing BSA fouling resistance by 25%.

Controlled post-assembly functionalization of nanoporous copolymer membranes that exhibit distinct multi-functionality

2019 Fall National Meeting

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