In situ polymerization of PPa@TpPa polyimine membranes for organic solvent nanofiltration

Compared with traditional polyamide membranes, polyimine membranes possess a more rigid structure and exhibit significantly enhanced swelling resistance in organic solvent nanofiltration, enabling highly selective separation. However, their intrinsic broad pore size distribution limits their application in high-precision separation scenarios. To address this issue, this study proposes a post-modification pore shrinkage strategy: first, a polyimine composite membrane is prepared via interfacial polymerization, followed by the in-situ polymerization of residual free p -phenylenediamine within the membrane initiated by ammonium persulfate, to construct an interpenetrating network composite membrane structure composed of porous polyimine and poly( p -phenylenediamine). Experimental results demonstrate that this method effectively improves the rejection performance of polyimine membranes toward small solute molecules. The optimized PPa-5@TpPa-2 composite membrane exhibits a methanol permeance of 4.1 L m −2  h −1  bar −1 , a molecular weight cut-off as low as 320 Da, along with excellent solvent resistance, operational stability.