Synthesis of perfluorinated carboxylic acid membrane monomers by utilizing liquid-phase direct fluorination

A new synthetic procedure for the preparation of perfluorinated carboxylic acid membrane monomers from non-fluorinated compounds has been developed. A key step in the synthetic route is liquid-phase direct fluorination reaction with elemental fluorine. Direct fluorination of a partially fluorinated diester, which was prepared from a hydrocarbon diol and a perfluorinated acyl fluoride, followed by thermal elimination, gave a perfluorinated diacyl fluoride, which is a precursor of a perfluorinated carboxylic acid membrane monomer.