TECHNOLOGY FOCUS - POLYMERS - Preferred Composition: The polymeric acid is an aryl main chain polymer having SO3H-, PO3H2-, COOH, or B(OH)2 groups or their salts and comprise polyethersulfone, polysulfone, polyphenylsulfone, polyetherethersulfone, polyetherketone, polyetheretherketone, polyphenylene ether, polydiphenylphenylene ether and/or polyphenylene sulfide. The salt, metal oxide or metal hydroxide is prepared by hydrolysis and/or a sol-gel reaction of a precursor, preferably an alkoxide/ester of Ti, Zr, Sn, Si, B or Al, a metal acetylacetonate, preferably Ti(acac)4 or Zr(acac)4 or is a mixed metal/element-alkoxide and metal acetyl acetonate, preferably Ti(acac)2(OiPr)2 or is an organic amine compound of Ti, Zr, Sn, Si, B or Al. The membrane is covalently cross-linked and is post treated with phosphoric acid to generate metal- or element phosphate or -hydrogen phosphate or -dihydrogen phosphate to contribute to proton conductivity.Preferred Process: A thin film is drawn from the polymer solution onto a support (glass or metal plate, textile, felt or porous (polymer)membrane) and the solvent evaporated at 80-150 degreesC at normal pressure or under vacuum and the resulting thin film is post-treated by the following steps which may be carried out in a variable order with the option of not carrying out steps (1), (2) and/or (3), where (1) in water at 50-100 degreesC, (2) in 1-100 wt.% mineral acid (hydrohalic acid, sulfuric acid or phosphoric acid) at 50-100 degreesC, (3) in 1-50 wt.% alkali (ammonia solution, amine solution, sodium hydroxide, potassium hydroxide, sodium carbonate solution, calcium hydroxide solution, barium hydroxide solution) or in an anhydrous liquid amine or mixture of amines, (4) in water at 50-100 degreesC. EXAMPLE - Sulfonated Victrex(RTM; poly(etheretherketone) (2 g, ion exchange capacity of 1.364 meq SO3H/g) was dissolved in N-methylpyrrolidinone (10 g) followed by the addition of triethylamine (1 g) and poly(4-vinylpyridine) (77 mg). A 75 wt.% solution of titanium (IV)-bis-acetylacetonato)diisopropylate in isopropanol (5.1 g) was then added and the mixture degassed prior to casting the solution onto a glass plate to form an 800 microm thick film. The film was then dried and removed from the glass plate in a water bath followed by treatment in 1N NaOH (24 h, 70 degreesC) and deionized water (24 h, 70 degreesC). The film (100 microm thick) was stored in deionized water at room temperature and had an ion exchange capacity of 1.15 meq SO3H/g, swelling value of 104 %, permselectivity (05 N/0.1 NaCl) of 78.35 % and resistance of 6.4 ohm-cm(0.5N HCl). An EDX spectrum of the film is depicted in the drawing and has a clear Ti signal.