Novel Polymer Electrolyte, Polymer Electrolyte Composition, Electrolyte Membrane, and Production Method and Use Thereof

Abstract

A polymer electrolyte comprising a hydrophilic segment having a sulfonic acid groups and a hydrophobic segment having no sulfonic acid group, each segment having an aromatic ring in its main chain, wherein the polymer electrolyte is an aromatic block copolymer having an ion-exchange capacity of solely the hydrophilic segment at 3.6 mmol/g or more, and an ion-exchange capacity of the block copolymer in the range of from 0.5 mmol/g to 3.0 mmol/g; a polymer electrolyte membrane produced from the polymer electrolyte and a fuel cell using thereof.

1 . A polymer electrolyte comprising a hydrophilic segment having a sulfonic acid groups and a hydrophobic segment having no sulfonic acid group, each segment having an aromatic ring in its main chain, wherein the polymer electrolyte is an aromatic block copolymer having
 an ion-exchange capacity IEC a  of solely the hydrophilic segment at 3.6 mmol/g or more calculated from the following equation, and   an ion-exchange capacity IEC of the block copolymer in the range of from 0.5 mmol/g to 3.0 mmol/g;   
     
       
         
           
             
               
                 
                   
                     IEC 
                     a 
                   
                   = 
                   
                     
                       IEC 
                       × 
                       W 
                     
                     
                       W 
                       a 
                     
                   
                 
               
               
                 
                   [ 
                   
                     Mathematical 
                      
                     
                         
                     
                      
                     1 
                   
                   ] 
                 
               
             
           
         
       
       wherein IEC is an ion-exchange capacity of the block copolymer, W is a weight of the block copolymer, and W a  is a weight of the hydrophilic segment in the block copolymer. 
     
   
   
       2 . The polymer electrolyte according to  claim 1 , wherein the aromatic block copolymer is an aromatic polyether block copolymer, and its hydrophobic segment has a structure represented by the following formula (1); 
     
       
         
         
             
             
         
       
       wherein D 1  is SO 2  or CO; Y 1  is O or S; and m is an integer of from 3 to 1,500. 
     
   
   
       3 . The polymer electrolyte according to  claim 1 , wherein the aromatic block copolymer is an aromatic polyether block copolymer, and its hydrophilic segment has a structural unit having a sulfonic acid groups incorporated into a structure represented by the following formula (2); 
     
       
         
         
             
             
         
       
       wherein D 2  is SO 2  or CO; Y 2  is O or S; and Ar 1  is a divalent aromatic residue. 
     
   
   
       4 . The polymer electrolyte according to  claim 1 , wherein the aromatic block copolymer is an aromatic polyether block copolymer, its hydrophilic segment has a structural unit [A] represented by the following formula (3) and a structural unit [B] represented by the following formula (4), and a weight ratio of [A]/[B] is in the range of from 10/0 to 1/9; 
     
       
         
         
             
             
         
       
       wherein D 3  is SO 2  or CO; b is an integer of 0 or 1, and at least either one of b is 1; Z is a hydrogen atom or an alkali metal; Y 3  is O or S; and Ar 2  is a divalent aromatic residue having a sulfonic acid group, 
     
     
       
         
         
             
             
         
       
       wherein D 4  is SO 2  or CO; Y 4  is O or S; and Ar 3  is a divalent aromatic residue having a sulfonic acid groups. 
     
   
   
       5 . The polymer electrolyte according to  claim 1 , wherein the aromatic block copolymer is an aromatic polyethersulfone block copolymer, wherein D 1 , D 2 , D 3  and D 4  are SO 2 , and Y 1 , Y 2 , Y 3  and Y 4  are 0 in the above formulas (1) to (4). 
   
   
       6 . The polymer electrolyte according to  claim 1 , having an ionic conductivity of 4×10 −3  S/cm or more at 50° C. and a relative humidity of 40%. 
   
   
       7 . The polymer electrolyte according to  claim 1 , having an ionic conductivity of 2×10 −3  S/cm or more at 70° C. and a relative humidity of 30%. 
   
   
       8 . A polymer electrolyte membrane comprising the polymer electrolyte according to  claim 1 , and having a thickness of from 5 μm to 200 μm. 
   
   
       9 . The polymer electrolyte membrane according to  claim 8 , comprising a phase-separation structure having an average distance between domains or lamellas of from 5 nm to 900 nm, when the membrane cross-section is observed with an electron microscope at a magnification of 90,000. 
   
   
       10 . The polymer electrolyte membrane according to  claim 8 , having an ionic conductivity of 4×10 −3  S/cm or more at 50° C. and a relative humidity of 40%. 
   
   
       11 . The polymer electrolyte membrane according to  claim 8 , having an ionic conductivity of 2×10 −3  S/cm or more at 70° C. and a relative humidity of 30%. 
   
   
       12 . A membrane/electrode assembly comprising the polymer electrolyte membrane according to  claim 8 . 
   
   
       13 . A membrane/electrode assembly comprising the polymer electrolyte according to  claim 1 . 
   
   
       14 . A solid polymer electrolyte fuel cell comprising the polymer electrolyte according to  claim 1 . 
   
   
       15 . A solid polymer electrolyte fuel cell comprising the membrane/electrode assembly according to  claim 12 . 
   
   
       16 . A direct liquid fuel injection-type fuel cell using the polymer electrolyte according to  claim 1 , comprising using alcohol or ether as a fuel. 
   
   
       17 . A direct liquid fuel injection-type fuel cell using the membrane/electrode assembly according to  claim 12 , comprising using alcohol or ether as a fuel. 
   
   
       18 . A polymer electrolyte composition comprising:
 a sulfonated block copolymer (A) composed of a hydrophilic segment having a sulfonic acid groups and a hydrophobic segment having no sulfonic acid group, each segment having an aromatic ring in its main chain; and   an aromatic polymer (B) having no sulfonic acid group and having the same structural unit as a structural unit contained in a hydrophobic segment of a sulfonated block copolymer;   wherein a weight fraction P b  of the aromatic polymer (B) is in the range of from 0.03 to 0.4 calculated from the following equation:   
     
       
         
           
             
               
                 
                   
                     P 
                     b 
                   
                   = 
                   
                     
                       
                         W 
                         B 
                       
                       
                         
                           W 
                           A 
                         
                         + 
                         
                           W 
                           B 
                         
                       
                     
                     . 
                   
                 
               
               
                 
                   [ 
                   
                     Mathematical 
                      
                     
                         
                     
                      
                     2 
                   
                   ] 
                 
               
             
           
         
       
       wherein W A  is a weight of the sulfonated block copolymer (A); and W B  is a weight of the aromatic polymer (B). 
     
   
   
       19 . The polymer electrolyte composition according to  claim 18 , wherein the aromatic polymer (B) is a block copolymer having a segment represented by the same structural formula as that of the hydrophobic segment of the sulfonated block copolymer. 
   
   
       20 . The polymer electrolyte composition according to  claim 18 , wherein the aromatic polymer (B) is a polymer represented by the same structural formula as that of the hydrophobic segment of the sulfonated block copolymer. 
   
   
       21 . The polymer electrolyte composition according to  claim 18 , wherein the sulfonated block copolymer (A) is an aromatic polyether block copolymer having a sulfonic acid groups. 
   
   
       22 . The polymer electrolyte composition according to  claim 18 , wherein the sulfonated block copolymer (A) contains a hydrophilic segment having a structural unit given by incorporating a sulfonic acid groups into a structure represented by the above formula (2). 
   
   
       23 . The polymer electrolyte composition according to  claim 18 , wherein the sulfonated block copolymer (A) contains a hydrophobic segment having a structure represented by the above formula (1). 
   
   
       24 . The polymer electrolyte composition according to  claim 18 , wherein the ion-exchange capacity of the sulfonated block copolymer (A) is in the range of from 0.6 mmol/g to 3.0 mmol/g, and the ion-exchange capacity of the composition is in the range of from 0.5 mmol/g to 2.9 mmol/g. 
   
   
       25 . The polymer electrolyte composition according to  claim 18 , wherein the sulfonated block copolymer (A) is a sulfonated block copolymer having
 an ion-exchange capacity IEC of solely the hydrophilic segment at 3.6 mmol/g or more, calculated from the following equation; and   an ion-exchange capacity IEC of the sulfonated block copolymer in the range of from 0.6 mmol/g to 3.0 mmol/g;   
     
       
         
           
             
               
                 
                   
                     IEC 
                     w 
                   
                   = 
                   
                     
                       IEC 
                       × 
                       W 
                     
                     
                       W 
                       w 
                     
                   
                 
               
               
                 
                   [ 
                   
                     Mathematical 
                      
                     
                         
                     
                      
                     3 
                   
                   ] 
                 
               
             
           
         
       
       wherein IEC W  is an ion-exchange capacity of the sulfonated block copolymer; W is a weight of the sulfonated block copolymer; and W W  is a weight of the hydrophilic segment in the sulfonated block copolymer. 
     
   
   
       26 . The polymer electrolyte composition according to  claim 18 , wherein the hydrophilic segment of the sulfonated block copolymer (A) has a structural unit [a] represented by the above formula (3) and a structural unit [b] represented by the above formula (4), and a weight ratio of [a]/[b] is in the range of from 10/0 to 1/9. 
   
   
       27 . The polymer electrolyte composition according to  claim 22 , wherein the sulfonated block copolymer (A) is an aromatic polyethersulfone block copolymer, wherein D 1 , D 2 , D 3  and D 4  are SO 2 , and Y 1 , Y 2 , Y 3  and Y 4  are 0 in the formula formulas (1) to (4). 
   
   
       28 . A polymer electrolyte membrane comprising the polymer electrolyte composition according to  claim 18 , and having a thickness of from 5 μm to 200 μm. 
   
   
       29 . A membrane/electrode assembly comprising using the polymer electrolyte composition according to  claim 18 . 
   
   
       30 . A membrane/electrode assembly comprising the polymer electrolyte membrane according to  claim 28 . 
   
   
       31 . A solid polymer electrolyte fuel cell comprising the polymer electrolyte composition according to  claim 18 . 
   
   
       32 . A solid polymer electrolyte fuel cell comprising the membrane/electrode assembly according to  claim 29 . 
   
   
       33 . A direct liquid fuel injection-type fuel cell using the polymer electrolyte composition according to  claim 18 , comprising using alcohol or ether as a fuel. 
   
   
       34 . A direct liquid fuel injection-type fuel cell using the membrane/electrode assembly according to  claim 29 , comprising using alcohol or ether as a fuel. 
   
   
       35 . A method for producing a sulfonated polyarylether block copolymer, comprising producing a sulfonated polyarylether block copolymer containing a hydrophobic segment having a structural unit represented by the following formula (5) and a hydrophilic segment having a structural unit having a sulfonic acid groups or derivative thereof incorporated into a structure represented by the following formula (6), wherein
 a hydrophilic segment prepolymer having a sulfonic acid groups in a potassium salt form and a hydrophobic segment prepolymer are block copolymerized;   
     
       
         
         
             
             
         
       
       wherein D 1  is SO 2  or CO; and Ar 1  is a divalent aromatic residue bonded an electron-withdrawing group in every aromatic ring belonging to Ar 1 , 
     
     
       
         
         
             
             
         
       
       wherein, D 2  is SO 2  or CO; and Ar 2  is a divalent aromatic residue. 
     
   
   
       36 . The method for producing a sulfonated polyarylether block copolymer according to  claim 35 , wherein a terminal hydroxyl group of the hydrophilic segment prepolymer is reacted in a form of a potassium salt. 
   
   
       37 . The method for producing a sulfonated polyarylether block copolymer according to  claim 35 , wherein the hydrophilic segment prepolymer is synthesized using a potassium salt of a divalent sulfonated aromatic dichloride compound represented by the following formula (7): 
     
       
         
         
             
             
         
       
       wherein D 2  is SO 2  or CO; p and q each are independently an integer of 0, 1, or 2; and p+q≧1. 
     
   
   
       38 . The method for producing a sulfonated polyarylether block copolymer according to  claim 35 , wherein the hydrophilic segment prepolymer has a structural unit [A] represented by the following formula (8) and a structural unit [B] represented by the following formula (9), and the weight ratio of [A]/[B] is in the range of from 10/0 to 1/9: 
     
       
         
         
             
             
         
       
       wherein D 2  is SO 2  or CO; p and q each are independently an integer of 0, 1, or 2; p+q≧1; and Ar 2  is a divalent aromatic residue, 
     
     
       
         
         
             
             
         
       
       wherein D 3  is SO 2  or CO; and Ar 3  is a divalent aromatic residue. 
     
   
   
       39 . The method for producing a sulfonated polyarylether block copolymer according to  claim 35 , wherein D 1 , D 2  and D 3  are SO 2  in the above formulas (5) to (9). 
   
   
       40 . The method for producing a sulfonated polyarylether block copolymer according to  claim 35 , wherein the hydrophobic prepolymer is a polyarylethersulfone represented by the following formula (10): 
     
       
         
         
             
             
         
       
       wherein D 4  is SO 2  or CO; and m is an integer of from 3 to 1,500. 
     
   
   
       41 . A method for producing a highly sulfonated polyarylether block copolymer, wherein a sulfonated polyarylether block copolymer produced by the production method according to  claim 35  is further sulfonated. 
   
   
       42 . A sulfonated polyarylether block copolymer produced by the production method according to  claim 35 . 
   
   
       43 . A proton conductor comprising using the sulfonated polyarylether block copolymer according to  claim 42 . 
   
   
       44 . A method for producing a polymer electrolyte membrane, comprising producing a polymer electrolyte membrane having a strong acid group or a superstrong acid group by casting, wherein
 a polymer electrolyte solution containing from 0.0005 to 2 parts by weight of a phosphate ester represented by the following formula (11) and/or a salt between an amine represented by the following formula (12) and a phosphate ester represented by the following formula (11) with respect to 100 parts by weight of a polymer electrolyte, is cast on a support, heated until a solvent of the solution is evaporated to form a self-supporting membrane, and the self-supporting membrane is peeled off from the support;   
     
       
         
         
             
             
         
       
       wherein R 1  is a hydrogen atom, an alkyl group having 6 to 18 carbon atoms, or a group represented by the following formula (13); and R 2  is an alkyl group having 6 to 18 carbon atoms or a group represented by the following formula (13), 
     
     
       
         
         
             
             
         
       
       wherein R 3  is an alkyl group having 5 to 18 carbon atoms; and m is an integer of from 2 to 30, 
     
     [Formula 13]
 wherein R 4  to R 6  each are a hydrogen atom, a hydroxyethyl 
 
     
       
         
         
             
             
         
       
     
     group, or an alkyl group having 1 to 12 carbon atoms. 
   
   
       45 . The method for producing a polymer electrolyte membrane according to  claim 44 , wherein the self-supporting membrane is further treated with an acid aqueous solution. 
   
   
       46 . The method for producing a polymer electrolyte membrane according to  claim 44 , wherein the self-supporting membrane is further treated with an alkali aqueous solution, and then with an acid aqueous solution. 
   
   
       47 . The method for producing a polymer electrolyte membrane according to claim  44 , wherein the polymer electrolyte is a hydrocarbon polymer electrolyte. 
   
   
       48 . The method for producing a polymer electrolyte membrane according to  claim 47 , wherein the hydrocarbon polymer electrolyte is an aromatic polymer electrolyte having an aromatic ring in its main chain. 
   
   
       49 . The method for producing a polymer electrolyte membrane according to  claim 48 , wherein the aromatic polymer electrolyte is an aromatic polyether having a structural unit represented by the following formula (14): 
     [Formula 14]
 wherein Ar 1  and Ar 2  each are an aromatic group; and Z 1  is
   —Ar 1 -Z 1 -Ar 2 -Z 1 -  (14) 
 
 
     an oxygen atom. 
   
   
       50 . The method for producing a polymer electrolyte membrane according to  claim 44 , wherein the polymer electrolyte is a composition of a polymer electrolyte having a sulfonic acid groups and a polymer having no sulfonic acid group. 
   
   
       51 . The method for producing a polymer electrolyte membrane according to  claim 44 , wherein the polymer electrolyte is a block copolymer containing a hydrophilic segment having a sulfonic acid groups and a hydrophobic segment having no sulfonic acid group. 
   
   
       52 . A polymer electrolyte membrane produced by the method for producing a polymer electrolyte membrane according to  claim 44 .