The invention relates to organic/inorganic hybrid polymer blends and hybrid polymer blend membranes that are composed of: one polymer acid halide containing SO.sub.2X, POX.sub.2 or COX groups (X.dbd., Cl, Br, I); one elemental or metallic oxide or hydroxide, obtained by the hydrolysis and/or the sol/gel reaction of an elemental and/or organometallic compound during the membrane forming process and/or by subsequently treating the membrane in aqueous acidic, alkaline or neutral electrolytes. The invention further relates to hybrid blends and hybrid blend membranes containing polymers that carry SO.sub.3H, PO.sub.3H.sub.2 and/or COOH groups, obtained by aqueous, alkaline or acidic hydrolysis of the polymer acid halides contained in the polymer blend or the polymer blend membrane. The invention also relates to methods for producing the inventive hybrid blends and hybrid blend membranes.