Imine-linked integrally crosslinked thin-film composite membrane for organic solvent nanofiltration

For thin-film composite (TFC) membranes applied in organic solvent nanofiltration (OSN), enhancing the adhesion between the active layers and the substrates can effectively improve the stability of the membranes. In this work, TFC OSN membranes with polyetherketone bearing amino group (PEK-NH₂) asymmetric substrates and amino-contained polyarylate active layers were fabricated by interfacial polymerization technique, and subsequently reacted with dialdehydes to form crosslinking between and within the substrates and the active layers. Crosslinking improved both of the solvent resistance of the substrates and the separation selectivity of the active layers. In addition, reverse pressure testing demonstrated that crosslinking allowed the active layers to adhere more strongly to the substrates. The optimized integrally crosslinked membranes exhibited methanol permeance of 10.4 L m⁻² h⁻¹ bar⁻¹ and a molecular weight cut-off of about 320 g mol⁻¹ in methanol. Moreover, the integrally crosslinked membranes maintained good stability for OSN operation in methanol for 12 days, and also exhibited unchanged OSN performance after soaked in N,N-dimethylformamide for 2 days. This work demonstrated a novel solvent-resistant membrane material and membrane-fabrication strategy with prospect for OSN application.