Quaternized fluorinated polyaryl ether anion exchange membranes with excellent dimensional stability for improved electrodialysis desalination

Ion exchange membranes have become indispensable in seawater desalination and wastewater treatment. However, traditional membranes with high ion exchange capacity suffer from excessive swelling. Meanwhile, overcoming the “trade-off” between membrane dimensional stability and ionic conductivity remains a critical challenge. In this work, a series of fluorinated polyaryl ether-based anion exchange membranes (AEMs) with varying hydrophobic chain content were designed. Results indicated that the incorporation of a rigid polymer backbone and the introduction of fluorinated groups exert a significant influence on the electrochemical properties of ion exchange membranes. The optimal QFPAE-x membrane exhibited good dimensional stability even at a high ion exchange capacity (IEC) of 2.16 mmol/g with a low swelling rate of 6.73 % at 25 °C. The membrane showed a surface resistance of 1.65 Ω·cm 2 and a water uptake of only 15.83 %. Furthermore, its cross-linking-free structure enabled superior dimensional stability and desalination performance. Electrodialysis desalination experiments show that the current efficiency and energy consumption perform better than commercial membranes. The cycle desalination experiments demonstrated the durability of the QFPAE-x membranes. This work demonstrates that fluorinated polyaryl ether AEMs with optimized hydrophobic chains effectively balance ion exchange capacity and dimensional stability, holding potential for efficient desalination and water treatment applications.