Highly chlorine-resistant end-group crosslinked sulfonated-fluorinated poly(arylene ether) for reverse osmosis membrane

Crosslinked (C-ESFx-BP) and non-crosslinked (N-ESFx-BP) sulfonated poly(arylene ether) (SPAE) membranes containing high fluorine contents were prepared as a function of the degree of sulfonation (DS) and evaluated for use as a highly potential chlorine-resistant reverse osmosis (RO) membrane. C-ESFx-BP membranes were obtained by covalent crosslinking among ethynyl end groups of the polymer chains via thermal curing. Both C-ESFx-BP and N-ESFx-BP membranes show the increase in NaCl rejection with decreasing DS, while water permeability declines due to the decrease of hydrophilicity. In particular, C-ESF70-BP membrane showed excellent salt (NaCl) rejection up to 98.4% compared with that of N-ESF70-BP membrane of 90.3% but showed slightly lower water permeability of 0.6 L μm/m2 h bar than that of 0.8 L μm/m2 h bar for N-ESF70-BP. Moreover, these C-ESFx-BP and N-ESFx-BP membranes displayed the long-term stability longer than 30 days during the operation condition under high acidic chlorine concentration of NaOCl 4000 ppm unlike commercial PA membranes which are unstable under the chlorine treatment. The stability comparison between them were observed by ATR-IR, retention ratio of molecular weight (RRMW), contact angle and X-ray photoelectron spectroscopy (XPS).