Hydrophilic and anti-fouling polyethersulfone ultrafiltration membranes with poly(2-hydroxyethyl methacrylate) grafted silica nanoparticles as additive

Here we report the preparation and properties of polyethersulfone (PES) ultrafiltration (UF) membranes with poly(2-hydroxyethyl methacrylate) (PHEMA) grafted silica (SiO2) nanoparticles (PHEMA@SiO2 NPs) as the blending additive. The PHEMA@SiO2 NPs were first prepared by grafting PHEMA brushes onto SiO2 NPs via a surface-initiated reversible addition fragmentation chain transfer (RAFT) polymerization. The organic–inorganic hybrid membranes of PES with PHEMA@SiO2 NPs were fabricated via the traditional non-solvent induced phase separation (NIPS) process. During membrane formation, the hydrophilic PHEMA@SiO2 NPs tended to migrate toward the membrane top surfaces. The membrane surface porosities were increased and the surface hydrophilicity was enhanced after introducing PHEMA@SiO2 NPs. More importantly, the water permeability, solute rejection and anti-fouling ability of PES membranes were improved significantly. This phenomenon indicated that the trade-off between permeability and selectivity of PES UF membranes was broken by the incorporation of PHEMA@SiO2 NPs. Different from traditional neat inorganic NPs additive, the PHEMA@SiO2 organic–inorganic NPs could be held in/on PES membrane for a long period of time due to the intertwisting of polymer chains. The present work provides a simple approach for stable and nearly permanent hydrophilization of PES UF membranes, which can also be extended to more membrane materials prepared by NIPS process.