Zwitterionic poly(arylene ether sulfone) copolymer/poly(arylene ether sulfone) blends for fouling-resistant desalination membranes

Zwitterionic polymers have drawn significant attention for membrane-based separations due to their impressive hydrophilicity and antifouling properties. Here we demonstrated a novel synthesis method to prepare an amphiphilic copolymer poly(arylene ether sulfone-co-sulfobetaine arylene ether sulfone) (PAES-co-SBAES), which was blended with native polysulfone (PSf) to prepare free standing membranes. The polymer chemical structures were analyzed by ¹H NMR spectroscopy and the molecular weight of polymers was identified by size exclusion chromatography (SEC). The PSf/PAES-co-SBAES blend membranes with various zwitterionic SBAES segment contents were fabricated via the non-solvent induced phase separation (NIPS) process. The membrane composition, surface morphology (roughness), and surface hydrophilicity were determined by fourier transform infrared (FT-IR) spectrum, atomic force microscopy (AFM), and water contact angle measurements, respectively. The cross-section morphology and surface hydrophilicity of the as-made membranes was analyzed by scanning electron microscopy (SEM) and water contact angle measurements, respectively. The results indicated that both the porosity of the support layer and surface hydrophilicity increased drastically due to the incorporation of hydrophilic SBAES segments. The water permeance and antifouling ability of the PSf/PAES-co-SBAES blend membranes were both remarkably improved to 2.5 L m⁻² h⁻¹ bar⁻¹ and 94% of flux recovery ratio, respectively, while salt rejection remained at a high level (98%) even under the high exposure to chlorine. This work provided a valuable and scalable strategy to fabricate desalination membranes via the introduction of zwitterionic segments in a rigid polysulfone matrix, and we predict that additional polymer optimization will drive the performance even higher.