Poly(fluorene-<i>co</i>-alkyl)-based PolymersBearing Pendant Piperidinium Cations for Alkaline Anion Exchange MembraneFuel Cell Applications

A series of ether-free poly(fluorene-<i>co</i>-alkyl) bearing pendant piperidinium cations (PFDPE-Pi and PFDPH-Pi) was synthesized by introducing alkyl spacers into the main chain. For comparison, quaternized poly(fluorene-<i>co</i>-triphenyl) without alkyl spacers was prepared and characterized under the same conditions. The introduction of flexible alkyl spacers imparted excellent flexibility, high water uptake, and high conductivity to the PFDPE-Pi and PFDPH-Pi membranes. Notably, the conductivity of PFDPH-Pi decreased by only 4% after immersion in 2 M KOH at 80 °C for 30 days, indicating its excellent alkaline stability. The H₂/O₂ anion exchange membrane fuel cell with PFDPH-Pi exhibited a peak power density of 698 mW cm^–2, which was significantly higher than that of 484 mW cm^–2 observed for the cells with PFTP-Pi. This study provides an effective approach for preparing durable polyfluorene-based anion exchange membranes with satisfactory comprehensive performance, highlighting their potential for fuel cell applications.