Anion conductive block poly(arylene ether)s: Synthesis, properties, and application in alkaline fuel cells

Anion conductive aromatic multiblock copolymers, poly(arylene ether)s containing quaternized ammonio-substituted fluorene groups, were synthesized via block copolycondensation of fluorene-containing (later hydrophilic) oligomers and linear hydrophobic oligomers, chloromethylation, quaternization, and ion-exchange reactions. The ammonio groups were selectively introduced onto the fluorene-containing units. The quaternized multiblock copolymers (QPEs) produced ductile, transparent membranes. A well-controlled multiblock structure was responsible for the developed hydrophobic/hydrophilic phase separation and interconnected ion transporting pathway, as confirmed by scanning transmission electron microscopic (STEM) observation. The ionomer membranes showed considerably higher hydroxide ion conductivities, up to 144 mS/cm at 80 °, than those of existing anion conductive ionomer membranes. The durabilities of the QPE membranes were evaluated under severe, accelerated-aging conditions, and minor degradation was recognized by ¹H NMR spectra. The QPE membrane retained high conductivity in hot water at 80 ° for 5000 h. A noble metal-free direct hydrazine fuel cell was operated with the QPE membrane at 80 °. The maximum power density, 297 mW/cm², was achieved at a current density of 826 mA/cm².