A chemical-induced crystallization strategy to fabricate poly(ether ether ketone) asymmetric membranes for organic solvent nanofiltration

Developing of polymeric material with high stability is the key to the progress of organic solvent nanofiltration (OSN) membranes. As a semi-crystalline polymer with rigid aromatic backbone structure, poly(ether ether ketone) (PEEK) has good resistance to most of the organic solvents. However, the preparation of PEEK asymmetric membranes is hindered by its inherent insolubility in common solvents. In this work, a chemical-induced crystallization (CIC) strategy involving fabrication of asymmetric membranes from its precursor polymer-poly(ether ether ketimine) (PEEKI) and then converting to PEEK by acid treatment was proposed. The results indicated that the obtained membranes could be used stably in various organic solvents, and the optimal membrane exhibited a DMF permeance of 4.19 L m-2 h-1 bar-1 and a molecular weight cut-off of 350 g mol−1 in DMF, which was an order of magnitude higher than the PEEK OSN membranes prepared from the sulfonic acid solvents. Meanwhile, the developed PEEK membranes also possessed good pressure resistance for long-term nanofiltration. Our study has proven the feasibility of fabrication PEEK asymmetric membranes through the CIC strategy for OSN application.