Reinforced ion-conductive membranes

Abstract

An ion-conductive membrane that includes a first layer comprising a first ionomer, and a porous polymer substrate, where at least a portion of the first ionomer is interpenetrated within the porous polymer substrate by ionomer-induced phase separation.

1 . An ion-conductive membrane comprising: 
 a first layer comprising a first ionomer; and    a porous polymer substrate, wherein at least a portion of the first ionomer is interpenetrated within the porous polymer substrate by ionomer-induced phase separation.    
   
   
       2 . The ion-conductive membrane of  claim 1 , wherein the first ionomer is interpenetrated within the porous polymer substrate in a substantially uniform manner.  
   
   
       3 . The ion-conductive membrane of  claim 1 , wherein the first ionomer comprises a sulfonated fluoropolymer.  
   
   
       4 . The ion-conductive membrane of  claim 1 , wherein the porous polymer substrate comprises a material selected from the group consisting of polysulfones, polyether imides, and combinations thereof.  
   
   
       5 . The ion-conductive membrane of  claim 1 , wherein the porous polymer substrate comprises a sulfonated porous polymer.  
   
   
       6 . The ion-conductive membrane of  claim 1 , wherein the porous polymer substrate comprises a polymer having a glass transition temperature of at least about 180° C.  
   
   
       7 . The ion-conductive membrane of  claim 1 , wherein the ion-conductive membrane has a membrane thickness of about 30 micrometers or less.  
   
   
       8 . The ion-conductive membrane of  claim 7 , wherein the ion-conductive membrane has a membrane thickness of about 15 micrometers or less.  
   
   
       9 . The ion-conductive membrane of  claim 1 , further comprising a second layer, the second layer comprising a second ionomer, wherein at least a portion of the second ionomer is interpenetrated within the porous polymer substrate by ionomer-induced phase separation.  
   
   
       10 . The ion-conductive membrane of  claim 9 , wherein the first ionomer and the second ionomer have different equivalent weights.  
   
   
       11 . The ion-conductive membrane of  claim 9 , wherein the first ionomer and the second ionomer each comprise a sulfonated fluoropolymer.  
   
   
       12 . A method of forming an ion-conductive membrane, the method comprising: 
 coating a first layer adjacent to a second layer, wherein the first layer comprises a first ionomer dispersed in a first solvent, and wherein the second layer comprises a reinforcement polymer substantially dissolved in a second solvent; and    initiating an ionomer-induced phase separation of the reinforcement polymer from the second solvent, thereby forming a porous polymer substrate from the reinforcement polymer and interpenetrating a portion of the first ionomer within the porous polymer substrate.    
   
   
       13 . The method of  claim 12 , wherein the second layer further comprises a second ionomer.  
   
   
       14 . The method of  claim 12 , wherein the step of coating the first layer adjacent to the second layer comprises coextruding the first layer and the second layer.  
   
   
       15 . The method of  claim 12 , wherein the first ionomer comprises a sulfonated fluoropolymer.  
   
   
       16 . The method of  claim 12 , wherein the reinforcement polymer comprises a material selected from the group consisting of polysulfones, polyether imides, and combinations thereof.  
   
   
       17 . The method of  claim 12 , further comprising coating the second layer with a third layer on an opposing surface of the second layer from the first layer, the third layer comprising a second ionomer dispersed in a third solvent, wherein the ionomer-induced phase separation further interpenetrates a portion of the second ionomer within the porous polymer substrate.  
   
   
       18 . A method of forming an ion-conductive membrane, the method comprising the steps of: 
 a) coating a first substrate layer having a first surface and a second surface from a first solution, the first solution comprising a reinforcement polymer substantially dissolved in a first solvent;    b) coating a first ionomer layer adjacent the first surface of the substrate layer, the first ionomer layer comprising a first ionomer;    c) coating a second ionomer layer adjacent the second surface of the substrate layer, the second ionomer layer comprising a second ionomer; and    d) initiating an ionomer-induced phase separation of the reinforcement polymer from the first solvent, thereby forming a porous polymer substrate from the substrate layer and interpenetrating a portion of the first ionomer and a portion of the second ionomer within the porous polymer substrate.    
   
   
       19 . The method of  claim 18 , wherein the first substrate layer, the first ionomer layer, and the second ionomer layer are coextruded.  
   
   
       20 . The method of  claim 18 , further comprising the steps of: 
 e) coating a second substrate layer having a first surface and a second surface from a second solution, the second solution comprising a second reinforcement polymer substantially dissolved in a second solvent;    f) coating a third ionomer layer adjacent the first surface of the second substrate layer, the third ionomer layer comprising a third ionomer;    g) coating a fourth ionomer layer adjacent the second surface of the second substrate layer, the fourth ionomer layer comprising a second ionomer;    wherein third ionomer layer is coated adjacent the second ionomer layer.    
   
   
       21 . The method of  claim 20  wherein step d) of initiating an ionomer-induced phase separation of the reinforcement polymer from the first solvent is carried out after step e) of coating a second substrate layer.  
   
   
       22 . The method of  claim 20  wherein step d) of initiating an ionomer-induced phase separation of the reinforcement polymer from the first solvent is carried out before step e) of coating a second substrate layer.  
   
   
       23 . The method of  claim 20 , wherein the first substrate layer, the first ionomer layer, the second ionomer layer, the second substrate layer, the third ionomer layer, and the fourth ionomer layer are coextruded.  
   
   
       24 . The method of  claim 20 , further comprising the step of: 
 h) initiating an ionomer-induced phase separation of the second reinforcement polymer from the second solvent, thereby forming a second porous polymer substrate from the second substrate layer and interpenetrating a portion of the third ionomer and a portion of the fourth ionomer within the second porous polymer substrate.    
   
   
       25 . A method comprising the step of laminating an ion-conductive membrane made according to the method of  claim 12  with a second ion-conductive membrane.  
   
   
       26 . A method comprising the step of laminating an ion-conductive membrane made according to the method of  claim 18  with a second ion-conductive membrane.