Novel branched sulfonated poly(phenylene sulfone)s for PEM-water electrolysis application

Sulfonated poly(phenylene sulfone)s (sPPS) are among the most promising candidates for proton exchange membrane (PEM) water electrolysis applications. However, challenges remain regarding their high water uptake and mechanical properties. To date, limited chemical architectures of sPPS have been reported, hindering the understanding of structure-property relationships. In this work, we present the first synthesis and characterization of low-degree branched poly(phenylene sulfone)s (b-sPPS) incorporating a hydrophobic branching segment. This branching strategy resulted in the highest molecular weight (Mw = 414 kg mol⁻¹) reported for sPPS polymers. Notably, branching did not result in increased water uptake or a significant change in mechanical properties compared to linear sPPS. Membranes of b-sPPS with 0.5 mol% branching degree and subsequent catalyst coated membranes (CCMs) were prepared and tested under PEM electrolysis conditions, outperforming Nafion™ N212 membranes under similar test conditions. Thus, we demonstrate that branching is an effective strategy for achieving high molecular weights without compromising the key properties of linear sPPS.