A regenerable thermo-responsive nanofiltration membrane with a molecularly anchored multilayer architecture for enhanced anti-scaling

This study fabricated a thermally self-cleaning nanofiltration membrane through molecular design and multi-scale assembly. PNIPAM-PEI microgels, synthesized by grafting PNIPAM and PEI, were deposited on a PPTA ultrafiltration substrate via layer-by-layer self-assembly. The deposition cycles were systematically optimized, followed by interfacial polymerization to form a polyamide separation layer. Characterization confirmed that five deposition cycles yielded a compact thermo-responsive intermediate layer and resulted in an interpenetrating [PEMs-PNIPAM]-PA structure. The resultant composite NF membrane exhibited excellent separation performance, with rejections of CaCl 2 and MgSO 4 reaching 97.3 % and 98.7 %, respectively, at 25 ℃, along with intelligent thermo-responsive behavior. When heated above the LCST, dehydration and contraction of the PNIPAM core drove the expansion of PA layer pores, activating a “pore expansion” self-cleaning mechanism, with full structural regeneration upon cooling. A 180-hour long-term test verified that high-temperature backwashing at 60 ℃ effectively restored the flux and retention of the fouled membrane. This work offers a new strategy for developing smart nanofiltration membranes with self-cleaning capability.