Polymer membrane, method for the production and use thereof

Abstract

The present invention relates to an acid-doped polymer membrane based on polyazoles, a process for producing it and its use. The acid-doped polymer membrane of the invention can be used in a variety of applications because of its excellent mechanical properties and is particularly useful as polymer electrolyte membrane (PEM) in PEM fuel cells.

1 . A doped polymer membrane based on polyazoles, obtainable by a process comprising the steps 
 A) casting a film using a solution of polymers based on polyazoles in a polar, aprotic organic solvent,    B) drying the film formed in step A) until it is self-supporting,    C) treating the film obtained in step B) with a treatment liquid at a temperature in the range from room temperature to the boiling point of the treatment liquid,    D) drying and/or dabbing the film treated according to step C) to remove the treatment liquid from step C),    E) doping the film treated according to step D) with a doping agdent.    
     
     
         2 . A polymer membrane as claimed in  claim 1  which is proton-conducting.  
     
     
         3 . A polymer membrane as claimed in  claim 1 , wherein the polymer based on polyazoles comprises recurring azole units of the formula (I) and/or (II)  
       
         
           
           
               
               
           
         
       
       where 
 Ar are identical or different and are each a tetravalent aromatic or heteroaromatic group which may have one or more rings,  
 Ar 1  are identical or different and are each a divalent aromatic or heteroaromatic group which may have one or more rings,  
 Ar 1  are identical or different and are each a trivalent aromatic or heteroaromatic group which may have one or more rings,  
 X are identical or different and are each oxygen, sulfur or an amino group which bears a hydrogen atom and a group having 1-20 carbon atoms, preferably a branched or unbranched alkyl or alkoxy group, or an aryl group as other radical.  
 
     
     
         4 . A polymer membrane as claimed in  claim 1 , wherein the polymer comprising recurring azole units is a copolymer comprising at least two units of the formula (I) and/or (II) which differ from one another.  
     
     
         5 . A polymer membrane as claimed in  claim 1 , wherein the polyazole consists only of units of the formula (I) and/or (II).  
     
     
         6 . A polymer membrane as claimed in  claim 1 , wherein the polyazole is a polymer comprising recurring benzimidazole units of the formula (III)  
       
         
           
           
               
               
           
         
       
       where n is an integer greater than or equal to 10, preferably greater than or equal to 100.  
     
     
         7 . A polymer membrane as claimed in  claim 1 , wherein the degree of doping is from 3 to 15 mol of acid per mol of recurring unit of the polymer.  
     
     
         8 . A membrane-electrode unit comprising at least one polymer membrane as claimed in  claim 1  and at least one electrode.  
     
     
         9 . A polymer electrolyte fuel cell comprising at least one membrane-electrode unit as claimed in  claim 8.