Synthesis and properties of multiblock ionomers containing densely functionalized hydrophilic blocks for anion exchange membranes

•Multiblock ionomers with densely functionalized hydrophilic blocks were synthesized.•The multiblock QPAESs membranes showed well-defined phase segregations.•The QPAESs membranes exhibited greatly enhanced hydroxide ion conductivity.•A feasible approach for fabrication of high performance AEMs was demonstrated.

A series of novel anion conductive multiblock ionomers, quaternized copoly(arylene ether sulfone)s (QPAESs) with sequential hydrophobic/hydrophilic structures and quaternary ammonium groups densely functionalized hydrophilic blocks, were successfully synthesized by chloromethylation, quaternization and alkalization of the parent copolymers. Hydrophilic precursor oligomers containing triphenyl methane moieties underwent block polycondensation with hydrophobic oligomers to provide the parent copolymers. We explored the influences of the block size of the hydrophobic/hydrophilic segments and functionalized degree of hydrophilic blocks on the morphology and properties of the obtained multiblock QPAESs membranes. The multiblock QPAESs membranes showed well-defined phase segregation. The QPAESs membranes demonstrated greatly enhanced hydroxide ion mobility due to the phase segregation and strong field effects of the dense functional clusters in hydrophilic blocks. The QPAESs membranes with higher densities of functional groups exhibited excellent hydroxide ion conductivity, moderate water uptakes and swelling ratios, excellent thermal properties, acceptable mechanical properties and good chemical stability. Especially, the QPAESs membranes with matched hydrophobic/hydrophilic blocks kept their appearances and kept their residual weights higher than 89% of the original values after treatment of 1 M NaOH solution at 60 °C for 132 days. These properties indicate the multiblock ionomers membranes are promising as anion exchange membranes of alkaline fuel cells.

Graphical abstractA series of novel anion conductive multiblock ionomers copoly(arylene ether sulfone)s with sequential hydrophobic/hydrophilic structure and quaternary ammonium groups densely functionalized hydrophilic blocks based on triphenyl methane moieties were successfully synthesized by chloromethylation, quaternization and alkalization of the precursor copolymers. The synergism of dense function groups per segment with size effect of the hydrophobic/hydrophilic blocks plays a key role in the aggregate structure and properties of the resulting polymers. The multiblock QPAESs membranes show well-defined phase segregations and greatly enhanced hydroxide ion mobility. The QPAESs membranes with higher functional groups densities exhibited excellent hydroxide ion conductivities, moderate water uptakes and swelling ratios, excellent thermal properties, acceptable mechanical properties and good chemical stability.Figure optionsDownload full-size imageDownload high-quality image (454 K)Download as PowerPoint slide