Quaternary ammonium containing poly(arylene ether sulfone) multi-block copolymers were synthesized via sequential nucleophilic polycondensation reaction, whereas the random copolymer ionomers were synthesized via one-pot step-growth reaction. 1H nuclear magnetic resonance was used to determine the composition, degree of functionalization (DF), and ion-exchange capacity (IEC) of poly(arylene ether sulfone) copolymers. Ionomers were processed into films by two separate methods: heterogeneous conversion and solution-casting. The hydrophilic and hydrophobic block lengths were found to have profound effect on the hydroxide conductivity, water uptake, swelling ratio, and tensile strength of the multi-block ionomer films. In general, multi-block ionomer films showed much higher hydroxide conductivity compared to random copolymer at an equivalent IEC. This was attributed to better ion-clustering in multi-block ionomer films. A percolation threshold associated with swelling was observed when equivalent ionomer’s IEC exceeded 2.02 meq/g. The maximum swelling observed for the multi-block copolymers was 33.6% at an IEC of 2.86 meq/g, which was much lower than the swelling observed in random copolymers with much smaller IECs. Such excellent swelling stability at high IEC was attributed to the sequential hydrophilic-hydrophobic block architecture. In addition, the solution-cast multi-block ionomer was determined to have the highest toughness (1185 x 104 J/m3), which was 237% greater than its heterogeneous counterpart. The results of this study suggest that block length and ionomer processing play a critical role in controlling swelling, improving mechanical strength, and enhancing ion transport.

Revisiting traditional anion exchange ionomer processing: Impact of solution-to-film evolution on ionomer properties

256th National Meeting (2018)

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