TECHNOLOGY FOCUS - POLYMERS - Preferred Components: The side chains of engineering aryl main chain polymers containing aromatic carboxylic acids, having tertiary basic N-groups (e.g. t-amines, pyridine, pyrimidine, triazine, imidazole, pyrazole, triazole, thiazole, oxazole etc., and all aromatic compounds with t-basic N groups) are modified by reaction with a metallized polymer P-Me in accordance with the reaction (B): where:P-Me + Ar-COOR' right arrow P-C(=O)-Ar + Me-O-R'P = a polymer with groups previously described:Ar = aromatic residue;Me = Na, Li;R = alkyl or aryl.The side chains of engineering aryl main chain polymers having aromatic sulfonic acid ester containing groups are modified by reacting the metallized polymer in accordance with the scheme (11a):P-Me + Ar-COX right arrow P-(=O)-Ar + Me-Xreaction of aromatic sulfonic ester derivative Ar-COX, e.g. a carboxylic acid ester COOR or an aromatic carboxylic acid halogenide Ar-COHal with a metallized polymer P-Me, in accordance with the scheme: (11b): sulfonation of the electrophile obtained at the side groups with H2SO4, SO3/P(O)(OR)3, ClSO3H, or sulfonation with another electrophilic sulfonation agent. The side groups are so selected that their sulfonation reactivity is higher than that of the main polymer chain reactivity for sulfonation. The engineering aryl main chain polymer has sulfonic acid functions only in the side chains. The base polymer for the polymer modification reaction is selected from the polyethersulfones: PSU Udel(RTM): R2(R3=CH3)-R4-R1(R3=H)-R5-R1-R4; PES Victrex (RTM): R1-R 5-R1-R4; PphSU Radel R (RTM)(R1(R3=H)-R1(R3=H)-R4-R1)(R3=H)-R5-R1-R4; PEES Radel A (RTM)((R-4-R-1(R-3=H)-R4-R1(R3=H)-R5-R1)(R3=H))n-(R4-R1(R3=H)-R5-R1(R3-H))m, n/m = 0.18. The base polymer for the modification reaction is PSU Udel (RTM). EXAMPLE - the compound bis(N,diethylamino)benzophenone was reacted with Li-PSU to give a reaction product (I), which was reacted with sulfonated PSU to give an acid-base blend membrane. Sulfonated PSU Udel (RTM) (4 g) in the SO3Li-form was dissolved in N-methylpyrrolidone (25 g). I (1 g) was added and stirred until dissolved. The dark brown solution obtained was filtered , degassed, transferred as a thin film to a glass plate, and the solvent was evaporated off. The glass plate was placed in a bath with desalinated water, and the polymer membrane formed was removed, was treated with 10% sulfuric acid at 70degreesC and then in desalinated water, and characterized. It had an exchange capacity of 1.365 meq SO3H/g and a specific resistance (in the H+ form) of 27.6 ohm.cm.