TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Components: The organic solvent is N-methyl-2-pyrrolidone (NMP), N,N-dimethylacetamide (DMAc), N,N-dimethylformamide (DMF), or dimethylsulfoxide (DMSO), and the drying agent is toluene or xylene.    TECHNOLOGY FOCUS - POLYMERS - Preparation (claimed): The co-polymer of formula (I) is prepared by reacting at elevated temperature in the presence of potassium carbonate, a compound resulting from polycondensation in the residue of a monomer of formulae (1)-(5), a sulfonated naphthalene diphenol monomer of formula (II), and a compound resulting from polycondensation in the residue of monomer of formula (III), -(Y-C-Y)c-.R, Y, C, a-d=have meanings as defined;X=H or alkali metal counterion consisting of Li+, Na+, K+, Rb+, or Cs+, or ammonium salt.Preferred Composition: The sulfur content (SC) of the co-polymer is 0.5-1. Preferred Process: The reaction is effected under inert gas atmosphere. An aprotic solvent and a drying agent are also present. The process additionally includes casting the co-polymer in the form of a membrane. The reaction is effected in a heating step to 130-140degreesC to de-hydrate, and increasing the temperature to 160-170degreesC to complete the reaction. Preferred Definitions: (i)X=H or alkali metal counterion consisting of Li+, Na+, K+, Rb+, or Cs+, or ammonium salt;    (ii)B and D=1,3-bis(4-benzoyl)-benzene, 1,4-bis(4-benzoyl)-benzene, or benzonitrile;    (iii)C=phenyl, biphenyl, naphthyl, or hexafluoro-isopropylidene-bisphenyl;    (iv)X=Na+ or H;    (v)    C=phenyl or biphenyl.    EXAMPLE - 1,3-Bis(4-fluorobenzoyl)benzene (BFBB, 5 mmol), sodium 6,7-dihydroxy-2-naphthalenesulfonate (DHNS, 31 mmol), 4,4'-biphenol (2 mmol), and potassium carbonate (7.5 mmol) were added into a flask and NMP (10 ml) and toluene (10 ml) were charged into the flask under argon atmosphere. The mixture was heated to 130-140degreesC. After dehydration and removal of toluene, the reaction temperature was increased to 160-170degreesC. When solution viscosity had increased, the mixture was cooled to 100degreesC and coagulated into a large excess of ethanol with vigorous stirring. After washing with ethanol twice, SPAEEKKs were purified for a week to remove salt.