Cross-linked aromatic polymers for high durability PEM membranes: materials and methods

Sulfonated aromatic polymers (SAP) are promising ionomer materials, however for applications as fuel cell membranes these polymers must be improved in terms of durability. The goal is to achieve a locally high density of functional groups such as sulfonic acid groups, but to keep the swelling low by appropriate cross- linking. Thermal cross-linking in presence of residual solvent dimethylsulfoxide without any addition of cross-linker molecules increases spectacularly the mechanical and hydrolytic stability of SAP, making them suitable for use up to 130 °C. The developed method is also inexpensive, being incorporated in the normal membrane casting procedure