Synthesis and properties of partially fluorinated poly(arylene ether) block copolymers containing ammonium groups as anion conductive membranes

Synthesis and properties of aromatic block copolymers containing fluorinated phenylene and biphenylene groups and ammonium-substituted fluorene groups are reported. High-molecular-weight poly(arylene ether) block copolymers were prepared from the corresponding telechelic oligomers and were chloromethylated. Quaternization reaction of the chloromethylated precursors with trimethylamine provided the title ammonium-substituted block copolymers (QPE-bl-4). The QPE-bl-4 membrane with the highest ion-exchange capacity (IEC = 1.3 mequivg^-1) showed high hydroxide ion conductivity (45 mS cm ^-1) at 80 °C due to its phase-separated morphology with interconnected ion-transporting pathway. The accelerated stability test in aqueous KOH solution containing hydrazine revealed that the ammonium groups decomposed to certain extent while the polymer main chains were rather robust to maintain the self-supporting membranes.