Effect of morphology on anion conductive properties in self-assembled polystyrene-based copolymer membranes

Polystyrene (PS) based random and block copolymers with trimethylammonium and azide side groups are synthesized via nitrogen mediated living radical polymerization. Anion exchange membranes (AEMs) are fabricated from the synthesized copolymers with hydrophobic and hydrophilic dialkyne crosslinkers using Click reaction. Morphological analysis by SAXS and TEM reveals the formation of ordered spherical nanostructure in the block copolymer membranes. In comparison with AEMs from the random copolymer, the block membranes show superior conductivity in higher KOH solutions despite their lower original IEC. The highest conductivity is obtained in 3 M KOH. No significant increase of water absorption or swelling is observed at elevated temperatures for any of the membranes, indicating their good mechanical integrity. No physical degradation is observed for the block membranes after 63 days in 8 M KOH at 60 °C. Fuel cell testing reveals that the block copolymer membranes with well-ordered nanostructure maintained better performance after 10 polarization curves compared to the commercially available AEM (A201)