Membranes with functionalized carbon nanotube pores for selective transport

Abstract

Provided herein composition and methods for nanoporous membranes comprising single walled, double walled, or multi-walled carbon nanotubes embedded in a matrix material. Average pore size of the carbon nanotube can be 6 nm or less. These membranes are a robust platform for the study of confined molecular transport, with applications in liquid and gas separations and chemical sensing including desalination, dialysis, and fabric formation.

1 . A process for the preparation of a membrane of selective permeability, said process comprising:
 (a) wetting with a first liquid phase a microporous support that is wettable by said first liquid phase, said first liquid phase having dissolved therein a first polymerizable species;   (b) contacting said microporous support thus wetted with a second liquid phase that is at least partially immiscible with said first liquid phase and in which is dissolved a second polymerizable species, one or both of said first and second liquid phases having carbon nanotubes randomly dispersed therein of an average length;   (c) causing said first and second polymerizable species to form a layer of a solid polymer over an outer surface of said microporous support;   (d) sealing said layer to form a substantially continuous barrier around said nanotubes, said barrier having a thickness that is less than said average length of said nanotubes; and   (e) recovering from said first and second liquid phases said microporous support with said layer adhering to said outer surface.   
     
     
         2 . The process of  claim 1 , wherein said first and second polymerizable species are mutually reactive by interfacial polymerization to form said solid polymer that is insoluble in said first and second liquid phases and that adheres to said microporous support. 
     
     
         3 . The process of  claim 1 , wherein steps (c) and (d) are performed in sequence, said layer of step (c) is defined as an intermediate layer and is a porous layer, and step (d) comprises forming an outer layer over said intermediate layer, said outer layer forming said barrier, and said outer layer having a thickness that is less than said average length of said nanotubes. 
     
     
         4 . The process of  claim 1 , wherein said carbon nanotubes are single-walled carbon nanotubes. 
     
     
         5 . The process of  claim 1 , wherein a ratio of said average length of said carbon nanotubes to said thickness of said layer is from about 1.3 to about 5. 
     
     
         6 . The process of  claim 1 , wherein said average length of said carbon nanotubes is from about 100 nm to about 2000 nm. 
     
     
         7 . The process of  claim 1 , wherein said carbon nanotubes have an inner diameter of about 0.4 nm to about 5 nm. 
     
     
         8 . The process of  claim 1 , wherein said microporous support is a member selected from the group consisting of polyethersulfone, polysulfone, nylon, and polyester, and said first liquid phase is a polar phase. 
     
     
         9 . The process of  claim 8 , wherein the second and optionally the third liquid phases are non-polar liquids. 
     
     
         10 . The process of  claim 1 , wherein said first liquid phase is a solution of said first polymerizable species in a polar solvent selected from the group consisting of water, an alcohol, and a glycol, and said second liquid phase is a solution of said second polymerizable species in a non-polar solvent selected from the group consisting of benzene, a halobenzene, an alkyl benzene, a C 5 -C 12  alkane, a halo-substituted C 5 -C 12  alkane, and an alkyl-substituted C 5 -C 12  alkane. 
     
     
         11 . The process of  claim 1 , wherein said first polymerizable species is an aromatic polyamine and said second polymerizable species is an aromatic polycarboxylic acid halide. 
     
     
         12 . The process of  claim 1 , wherein said first polymerizable species is m-phenylenediamine and said second polymerizable species is trimesoyl chloride. 
     
     
         13 . A process for the preparation of a membrane of selective permeability, said process comprising:
 (a) wetting with an aqueous phase a microporous support selected from polysulfone or polyethersulfone that is wettable by said aqueous phase, said aqueous phase having dissolved therein m-phenylenediamine;   (b) contacting said microporous support thus wetted with a solvent phase that is at least partially immiscible with said aqueous phase and in which is dissolved trimesoyl chloride, one or both of said aqueous and solvent phases having carbon nanotubes randomly dispersed therein of an average length;   (c) causing said m-phenylenediamine and trimesoyl chloride to form a layer of a solid polymer over an outer surface of said microporous support;   (d) sealing said layer to form a substantially continuous barrier around said nanotubes, said barrier having a thickness that is less than said average length of said nanotubes; and   (e) recovering from said aqueous and solvent phases said microporous support with said layer adhering to said outer surface.   
     
     
         14 . A membrane of carbon nanotubes formed by the process of  claim 1 . 
     
     
         15 . A membrane with embedded carbon nanotubes, said membrane comprising a plurality of carbon nanotubes open at both ends and embedded in a solid, substantially continuous polymeric matrix, said polymeric matrix having a thickness that is less than an average of the lengths of said carbon nanotubes, said carbon nanotubes having substantially random orientations relative to said membrane and yet oriented such that at least a portion of said plurality of carbon nanotubes have both open ends protruding from said membrane to provide fluid communication through said membrane. 
     
     
         16 . The membrane of  claim 14 , further comprising a layer of microporous material supporting said polymeric matrix. 
     
     
         17 . The membrane of  claim 14 , wherein a ratio of said average of the lengths of said carbon nanotubes to said thickness of said polymeric matrix is from about 1.3 to about 5. 
     
     
         18 . A method for desalination of water, said method comprising passing said water through a membrane comprising a plurality of nanotubes open at both ends and embedded in a solid, substantially continuous polymeric matrix, said polymeric matrix having a thickness that is less than an average of the lengths of said nanotubes, said nanotubes having substantially random orientations relative to said membrane and yet oriented such that at least a portion of said plurality of nanotubes have both open ends protruding from said membrane to provide fluid communication through said membrane. 
     
     
         19 . The method of  claim 18 , wherein said membrane further comprises a layer of microporous material supporting said polymeric matrix. 
     
     
         20 . The method of  claim 18 , wherein the ratio of said average of the lengths of said nanotubes to said thickness of said polymeric matrix is from about 1.3 to about 5. 
     
     
         21 . The method of  claim 18 , wherein said polymeric matrix has a substantially planar exposed outer surface and contains from about 2.5×10 8  to about 1×10 12  nanotubes per square centimeter of said exposed outer surface.