Direct aromatic nucleophilic substitution polycondensations of disodium 3,3'-disulfonate-4,4'-difluorodiphenylsulfone (SDFDPS), 4,4'-difluorodiphenylsulfone (DFDPS) (or their chlorinated analogs), and 4,4'-thiobisbenzenethiol in the presence of potassium carbonate were investigated. Electrophilic aromatic substitution was employed to synthesize the SDFDPS comonomer in high yields and purity. High molecular weight disulfonated copolymers were easily obtained using the SDFDPS monomers, but in general, slower rates and a lower molecular weight copolymer were obtained using the analogous chlorinated monomers. Tough and ductile membranes were solution cast from N,N-dimethylacetamide for both series of copolymers. The degrees of disulfonation (20-50%) were controlled by varying the ratio of disulfonated to unsulfonated comonomers. Precise control of the ionic concentration, well-defined ionic locations, and enhanced stability due to the deactivated position of the -SO3H group are some of the suggested advantages of direct copolymerization of sulfonated monomers. Further publications will discuss additional characteristics of these copolymers that have the same repeat unit, but different molecular weights, using methanol permeability, water uptake, protonic conductivity, and dynamic mechanical analysis. (c) 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2964-2976, 2005.