Synthesis and Properties of a Multiblock Copolymer with Long Side Chains for Anion Exchange Membrane Fuel Cells

Anion Exchange Membrane (AEM) fuel cells are a possible route to overcoming fundamental issues with acid-based fuel cells. The issues include the high cost of platinum catalysts, complex water transport, and sluggish electrochemical reactions, etc. However, the performance of AEM fuel cells is not as good as that of Proton Exchange Membrane (PEM) fuel cells because of the limitations of current anion exchange membranes, such as low ionic conductivity, poor stability at high pH, and high water uptake.

A series of novel multiblock copoly(arylene ether)s with long side chains were synthesized for AEM fuel cells. The multiblock copolymers were synthesized by polycondensation of separately-prepared hydroxyl-terminated oligomers with fluoro-terminated oligomers. The resulting multiblock structure, in which one block is hydrophilic and one block is hydrophobic, was designed to ensure a nanophase-separated morphology. Multiblock copolymers with different block lengths and ion exchange capacities (IEC) were synthesized to maximize ion conductivity and explore the relationship between chemical structures and properties in anion exchange membranes. Furthermore, copolymers with long side chains exhibited higher stability in high pH environment than their counterparts without long side chains. The degradation mechanism was also studied for the long side chain block copolymers.

Financial support from US Office of the Deputy Assistant Secretary of the Army for Defense Exports and Cooperation (DASA-DE&C) is gratefully acknowledged.