A simple and cost-efficient route to prepare sulfonated dihalo-monomers for synthesizing sulfonated aromatic PEMs.

We present a simple and cost-efficient route for the preparation of sulfonated dihalo-monomers for the synthesis of hydrocarbon ionomers. After conventional monomer sulfonation, excess sulfuric acid is quantitatively removed by neutralization with BaCO. This leads to the precipitation of excess HSO as insoluble BaSO, which is easily separated from the sulfonated monomers in their soluble Ba-forms by filtration.