High permeance of BAHFP-PA membrane prepared by cosolvent assisted interfacial polymerization

Constructing polyamide (PA) separation layers from rigid, three-dimensionally twisted aromatic diamine monomers is a promising route toward high-permeance organic solvent nanofiltration (OSN) membranes. However, the poor water solubility of such monomers limits their application in conventional aqueous interfacial polymerization (IP). Herein, water/DMF cosolvent assisted interfacial polymerization strategy was adopted to address this bottleneck. The poorly water-soluble 2,2-bis(4-aminophenyl) hexafluoropropane (BAHFP) monomer can solve in water/DMF co-solvent and get controlled monomer diffusion and IP kinetics to form an ultra-thin, defect-free polyamide active layer. The introduction of DMF enhances the solubility of BAHFP with three-dimensional twisted configuration. A minor quantity of 50 wt%  N , N -dimethylformamide (DMF) was introduced into the water as a cosolvent, facilitating the formation of a continuous polyamide (PA) layer with a thickness of 85.7 ± 3.5 nm on the surface of the composite membrane. Additionally, the membrane prepared at the optimal DMF concentration of 60% exhibited the continuous and complete PA film and a methanol permeability of 28.3 ± 0.4 L m −2  h −1  bar −1 and 98.7 ± 0.3% rejection of RB for 30 h. The smoother top surface significantly improves the membrane's anti-fouling properties. This work offers an effective way for the fabrication of high permeance BAHFP-PA membrane through IP process.