Sulfonated Low-Cost Ionomers as Acidic Cross-Linkers for High-Temperature PBIOO Membranes

Abstract

The low-cost polymers poly(styrene) and poly(α-methylstyrene) have been sulfonated in a first step. Then both sulfonated ionomers have been blended with PBIOO® (30 wt% sulfonated ionomer, 70 wt% PBIOO), the sulfonated ionomer serving as acidic cross-linker which enhances the PBIOO stability. Both membrane types were treated with Fentons Reagent to investigate their oxidative stability. Of particular interest was whether the poly(α-methylstyrene) ionomer was more stable against radical attack. It was indeed found that the PBIOO-sulfonated poly(α-methylstyrene) blend membrane showed less weight loss during and after Fenton Test than the respective poly(styrene sulfonic acid) PBIOO-containing membrane. The macromolecules are partially degrading by radical attack to the main chain of the sulfonated poly(α-methylstyrene) polymers but still remain in the blend membrane matrix due to acid-base interactions. Since the PBIOO/sulfonated poly(α-methylstyrene) blend membranes conserved their integrity even after Fentons Test they can be regarded as interesting low-cost high-T fuel cell membranes.