Crosslinked polyimide membranes for organic-solvent nanofiltration: Achieving high performance and chemical stability through bromine-based crosslinking

Abstract

This study presents the development of an organic solvent nanofiltration (OSN) membrane with enhanced chemical and alkaline resistance, achieved through the crosslinking of brominated polyimide. By leveraging the high reactivity of bromine, two pyridyl crosslinking agents of varying lengths were effectively integrated into the membrane structure. The DP-PI membrane crosslinked with longer linker exhibited approximately double the permeance of the BP-PI membrane with shorter linker, attributed to structural differences resulting from the length of the crosslinking agents. Meanwhile, the BP-PI membrane demonstrated superior rejection due to its denser crosslinked structure. Under alkaline solvent conditions, both membranes showed partial swelling, leading to reduced rejection. Despite these changes, the membranes maintained stable performance over 80 h, highlighting their strong resistance to harsh alkaline environments. Our bromination-substitution crosslinking strategy effectively forms robust covalent bonds while preserving the integrity of the imide rings, significantly enhancing the membranes' durability. These findings position crosslinked polyimide membranes as highly promising candidates for OSN applications, combining excellent chemical stability, high selectivity, and robust performance.