Thermal treatment of functionalized carbon nanotubes in solution to effect their functionalization

Abstract

The present invention is directed towards methods of thermally defunctionalizing functionalized (derivatized) carbon nanotubes (CNTs) in solution or suspended in a liquid medium. Such defunctionalization largely comprises the removal of sidewall functionality from the CNTs, but can also serve to remove functionality from the CNT ends. Such methods facilitate the resuspension of such defunctionalized CNTs in various solvents and permit the defunctionalization of functionalized CNTs that would normally decompose (or partially decompose) upon thermal treatment. Such methods of defunctionalization can typically lead to defunctionalized CNTs that are essentially pristine (or nearly pristine), and which, in contrast to prior art methods of thermal defunctionalization, can be easily resuspended in a variety of solvents.

1 . A method comprising the steps of: 
 (a) suspending a quantity of functionalized carbon nanotubes in a solvent to form a suspension of functionalized carbon nanotubes; and    (b) heating said suspension to a temperature that will thermally defunctionalize the functionalized carbon nanotubes yielding a defunctionalized product.    
     
     
         2 . The method of  claim 1 , wherein the carbon nanotubes are selected from the group consisting of single-wall carbon nanotubes (SWNTs), multi-wall carbon nanotubes (MWNTs), double-wall carbon nanotubes, semiconducting carbon nanotubes, metallic carbon nanotubes, semi-metallic carbon nanotubes, chiral carbon nanotubes, buckytubes, carbon fibrils, and combinations thereof.  
     
     
         3 . The method of  claim 1 , wherein the solvent is thermally stable at the temperatures required for defunctionalization.  
     
     
         4 . The method of  claim 1 , wherein the solvent is selected from the group consisting of o-dichlorobenzene, benzene, toluene, water, sulfuric acid, oleum, sulfuric acid with dissolved potassium persulfate, liquid ammonia, liquid ammonia with dissolved alkali metals, alkanes, parafins, thiophene, and combinations thereof.  
     
     
         5 . The method of  claim 1 , wherein the suspension is completely enclosed in a vessel.  
     
     
         6 . The method of  claim 1 , wherein the suspension further comprises a polymeric species.  
     
     
         7 . The method of  claim 1 , wherein the suspension further comprises a surfactant.  
     
     
         8 . The method of  claim 1 , wherein the defunctionalized product is selected from the group consisting of unfunctionalized carbon nanotubes, partially functionalized carbon nanotubes, and combinations thereof.  
     
     
         9 . The method of  claim 1 , wherein the defunctionalized product is functionally uniform.  
     
     
         10 . The method of  claim 1 , wherein the defunctionalized product is resuspendable in a solvent.  
     
     
         11 . The method of  claim 1 , wherein the functionalized carbon nanotubes are selectively defunctionalized according to different (n,m) types, said types displaying differential propensity for defunctionalization.  
     
     
         12 . A method comprising the steps of: 
 (a) dispersing a quantity of functionalized carbon nanotubes in a polymer matrix to form a first blended material comprising functionalized carbon nanotubes in a polymer host; and    (b) heating said first blended material to a temperature that will thermally defunctionalize the functionalized carbon nanotubes with the polymer host to yield a second blended material comprising defunctionalized or partially defunctionalized carbon nanotubes in a polymer host.    
     
     
         13 . The method of  claim 12 , wherein the carbon nanotubes are selected from the group consisting of single-wall carbon nanotubes (SWNTs), multi-wall carbon nanotubes (MWNTs), double-wall carbon nanotubes, semiconducting carbon nanotubes, metallic carbon nanotubes, semi-metallic carbon nanotubes, chiral carbon nanotubes, buckytubes, carbon fibrils, and combinations thereof  
     
     
         14 . The method of  claim 12 , wherein the defunctionalized carbon nanotubes are selected from the group consisting of unfunctionalized carbon nanotubes, partially functionalized carbon nanotubes, and combinations thereof.