A Thermosensitive Block Copolymer Based Ultrafiltration Membrane with Adjustable Pore Size for Self-Cleaning and Antifouling

Antifouling is a worldwide challenge in the industrial application of ultrafiltration membranes. We report in this work the synthesis of a poly(vinylidenefluoride)-block-poly(N-isopropylacrylamide) (PVDF-b-PNIPAAm) block copolymer and its application in modifying poly(vinylidenefluoride) (PVDF) membranes to enhance their antifouling performance. The copolymer enables temperature-controlled pore size adjustment via lower critical solution temperature (LCST) behavior on membrane surfaces. Above LCST, pore expansion facilitates contaminant removal through water washing, while sub-LCST temperatures restore original pore dimensions, significantly reducing irreversible fouling. After repeated backwashing above the LCST, the flux recovery rate (FRR) of the PVDF-b-PNIPAAm-modified PVDF ultrafiltration membrane remained consistently above 90%, indicating outstanding cleanability and reusability. Furthermore, the PVDF-b-PNIPAAm block copolymer synthesized by iodine transfer polymerization exhibits excellent miscibility with commercial PVDF, leading to significant improvements in the hydrophilicity, surface micropore density, and pure water flux. Our work highlights the great potential of antifouling PVDF-based ultrafiltration membranes for water treatment and provides a technical foundation for the mass production of sustainable antifouling membranes.