The present invention relates to polymer films and a polymer membrane having an improved mechanical property profile produced therefrom, to a process for producing them and to their use. The polymer films, polymer membranes and separation membranes of the invention are produced from selected polymer raw materials and have excellent chemical, thermal. and mechanical properties as are required for use as polymer electrolyte membranes (PEMs) in PEM fuel cells or in apparatuses for the filtration and/or separation of gases and/or liquids or for reverse osmosis.