The copolymerization of 5-[(4-fluorophenyl)sulfonyl]-2-fluorobenzo acid with bis(4-hydroxyphenyl)sulfone in 1,1-dioxothiolane with sodium carbonate as a base results in carboxylated poly(ether sulfone)s. The polycondensation polymerization, however, is associated with partial decarboxytation. Conversely, the copolymerization of 2,5-dihydroxybenzoic acid (hydroquinone carboxylic acid) with bis(4-fluorophenyl)sulfone under identical conditions results in a poly(ether ether sulfone) with quantitative decarboxylation.