(342d) Antifouling Membranes: Preparation and Applications

A major obstacle restricting the wide application of ultrafiltration (UF) is membrane fouling. Due to the intrinsic drawbacks of surface graft polymerization modification, we focused on the surface segregation method to fabricate efficacious antifouling brush layer, in hopes of achieving in-situ and three-dimensional surface modification (including membrane surface and internal pores) during the non-solvent induced phase separation membrane formation process. The surface modification agents (SMA) included amphiphilic poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (Pluronic) and zwitterionic block copolymers. The hydrophobic segments in the copolymers ensured the firm anchorage of SMA in the membrane matrix, while the hydrophilic chains endowed the membranes surface with higher hydrophilicity. Order-of-magnitude flux enhancement, complete resistance to irreversible fouling and desirable long-term recycling property were demonstrated when the resultant UF membranes were utilized for protein solutions concentration or fractionation and oil-water emulsion separation. Sum-frequency generation vibrational spectroscopy (SFG), X-ray photoelectron spectroscopy (XPS) and molecular simulation technology were carried out to investigate fouling resistance mechanism at molecular level. The results showed that in air the hydrophobic material or segment would cover the film surface, while the hydrophilic counterparts were buried within polymer matrix. Upon water exposure, the hydrophilic segments tended to segregate to surface and fully extend in water. The structure of water molecules near zwitterionic surface was also studied and the results provided direct evidence for the hydration layer antifouling mechanism.