Anion-exchange membranes based on poly(arylene ether ketone) with pendant quaternary ammonium groups for alkaline fuel cell application

• PAEK with pendant quaternary ammonium groups was synthesized.
• PAEK was aminated with TMA, TEA, and TPA to examine alkyl length effect.
• PAEK-TMA illustrated higher conductivity due to less steric hindrance.
• High anion conductivity was observed while low water uptake was maintained.

Poly(arylene ether ketone)s (PAEKs) with pendant quaternary ammonium groups were synthesized via a direct step-growth polycondensation reaction to prepare anion exchange membranes (AEMs) for alkaline fuel cells. The chemical structure of the synthesized quaternary ammonium PAEK was confirmed by 1H nuclear magnetic resonance spectroscopy (1H NMR), Fourier transform infrared (FT-IR) spectroscopy and energy dispersive X-ray (EDX) spectroscopy. Three types of PAEK based membrane with different alkyl chain lengths in the amine core were synthesized and their properties were compared. The anion conductivity of the prepared PAEK membranes decreased with aminated alkyl length. The membranes aminated with the trimethylamine (PAEK-TMA), triethylamine (PAEK-TEA), tripropylamine (PAEK-TPA) 0.014, 0.003, and 0.0008 Scm−1 at 40 °C and 0.021, 0.006, and 0.0014 Scm−1 at 80 °C, respectively. While the PAEK-TMA, PAEK-TEA, and PAEK-TPA membranes exhibited different ionic conductivities, they showed quite low water uptake −15.8% at 30 °C and 26.9% at 90 °C for PAEK-TMA, 11% at 30 °C and 17.6% at 90 °C for PAEK-TEA, 10.7% at 30 °C and 16.5% at 90 °C for PAEK-TPA. Such high anion conductivity and low water uptake of the prepared membranes are potential advantages for their application in AEMs.