Bridging the miscibility gap to fabricate delamination-free dual-layer nanofiltration membranes via incorporating fluoro substituted aromatic amine

Delamination of the dual-layer membrane fabricated from immiscible polymers is recognized as the main obstacle to advance the technology. The current work discloses an innovative approach to address the delamination issue by incorporating specific functional groups on the polymer chains. Delamination-free P84®/Ultem® dual-layer hollow fiber nanofiltration membranes were obtained by incorporating 4-Fluoro-2-(trifluoromethyl) benzylamine (FTB) in P84® polyimide. The progressively incorporated FTB on P84® decreases solubility parameter difference and establishes specific intermolecular interactions between the polymer pair which contributes to the interpenetration of molecules at the interfacial region of the dual layers. The interpenetrated network structure at the interfacial region renders the robust integrity of the dual-layer membranes. The one-step fabricated membranes had an over 99% rejection of tetracycline (MW: 444.4 Da) in methanol with pure methanol permeance of 3.7 LMH/bar. The elaborated mechanism may potentially enlarge the scope of selecting immiscible polymers for fabricating dual-layer membranes by molecular designing.