Antifouling Membranes and Stable Liquid-Infused Membranes Enabled by Fluoro-Polydopamine

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In this study, a dopamine derivative was synthesized and employed to yield self-adhering coatings that enabled both strong bacteria resistance and the fabrication of stable liquid-infused membranes (LIMs). First, nuclear magnetic resonance spectroscopy was used to confirm that a long fluoro-chain tail was successfully introduced to dopamine, forming fluoro-tailed dopamine (f-DOPA). A one-step process was next used to self-polymerize f-DOPA into a self-adhering coating of fluoro-polydopamine (f-PDA) on poly(ether sulfone) (PES) ultrafiltration membranes, as confirmed using X-ray photoelectron spectroscopy. The pure water permeance of the f-PDA-coated membranes prepared at three different reaction times was benchmarked against controls that included bare PES membranes and polydopamine (PDA)-coated membranes. Antifouling assays revealed that the f-PDA membranes reduced the attachment of Escherichia coli K12 by up to 70% compared to unmodified PES membranes. As a proof-of-concept, we demonstrated that LIMs, which mimic the Nepenthes pitcher plant, can be formed by immobilizing perfluoropolyether oils on the f-PDA-coated PES membranes. Remarkably, f-PDA LIMs exhibited stable permeance over five filtration cycles. In sum, this work demonstrates that the mussel-inspired dopamine derivative presents a new approach to creating high-performance, antifouling membranes appropriate for a wide range of separations.