Backbone stability of quaternized polyaromatics for alkaline membrane fuel cells

Abstract

The backbone stability of benzyl-trimethyl ammonium (BTMA) functionalized polyaromatics was investigated in two structurally differing polymer architectures; quaternized poly(arylene ether) (PAE) and poly(phenylene) (PP). FTIR analysis indicated the cleavage of aryl-ether linkages in quaternized PAEs under high pH environments, while no backbone degradation in quaternized PP was observed. The backbone degradation of PAEs not only significantly reduced the mechanical properties of the membranes, but also negatively impacted hydroxide conductivity. Membrane electrode assemblies (MEAs) using both PAE and PP membranes showed good initial alkaline membrane fuel cell performance. However, the PAE MEA displayed larger performance losses and failure after only 55h, due to a mechanical breach. No catastrophic failure of the PP MEA occurred after 300h, which further confirmed the stability of the polymer backbone.