High performance sulfonated aromatic ionomers by solvothermal macromolecular synthesis

Thermal cross-linking in presence of residual solvent dimethylsulfoxide without any addition of cross-linker molecules is described. This elegant method increases spectacularly the mechanical and hydrolytic stability of sulfonated aromatic polymers (SAP), making them suitable for use in liquid water also at 145 °C. Data on water uptake, mechanical properties and proton conductivity are presented and discussed from a bond energy point of view. The developed method is also inexpensive, being incorporated in the normal membrane casting procedure. This opens new horizons and hitherto conventionally disregarded SAP membranes should be reconsidered as fuel cell membranes. ► Thermal cross-linking occurred in Sulfonated Aromatic Polymers in presence of DMSO without cross-linker. ► Formation of covalent sulfone bridges between chains improves hydrolytic stability. ► Morphological changes caused by annealing improve mechanical properties.