Towards highly conducting and stable poly(fluorenyl biphenyl)-based anion exchange membranes by grafting dual Y-shaped side-chains

High hydroxide conductivity and sufficient dimensional/alkaline/mechanical stability are highly desired for practical applications of anion exchange membranes (AEMs). Herein, a new di-quaternized side-chain precursor (EDQA) was firstly designed and synthesized. Then novel AEMs (DBTF-4QA-x) based on poly(fluorenylene alkylene)s containing dual Y-shaped side-chains were prepared from EDQA by an efficient click reaction. Benefiting from several structural advantages of EDQA, DBTF-4QA-x membranes possessed high hydroxide conductivities up to 154.8 mS cm−1 at 80 °C, while maintained high dimensional stability. The membranes exhibited robust mechanical properties with tensile strengths and elongation at break up to 107.4 MPa and 46.4%, respectively. Furthermore, the membranes showed high alkaline stability with the conductivity loss below 11.4% after immersing in 4 M aq. NaOH at 80 °C for 40 days. In addition, DBTF-4QA-0.5 membrane achieved the maximum peak power density of 836.4 mW cm−2 in H2/O2 fuel cells at 60 °C.