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The present invention is directed to methods of integrating carbon nanotubes into epoxy polymer composites via chemical functionalization of carbon nanotubes, and to the carbon nanotube-epoxy polymer composites produced by such methods. Integration is enhanced through improved dispersion and/or cova

The present invention is directed to methods of integrating carbon nanotubes into epoxy polymer composites via chemical functionalization of carbon nanotubes, and to the carbon nanotube-epoxy polymer composites produced by such methods. Integration is enhanced through improved dispersion and/or covalent bonding with the epoxy matrix during the curing process. In general, such methods involve the attachment of chemical moieties (i.e., functional groups) to the sidewall and/or end-cap of carbon nanotubes such that the chemical moieties react with either the epoxy precursor(s) or the curing agent(s) (or both) during the curing process. Additionally, in some embodiments, these or additional chemical moieties can function to facilitate dispersion of the carbon nanotubes by decreasing the van der Waals attractive forces between the nanotubes.

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What is claimed is: 1. A method comprising the steps of: a) dispersing functionalized CNTs in a solvent to form a dispersion; wherein the functionalized CNTs comprise oxidized, fluorinated CNTs; wherein the oxidized, fluorinated CNTs are prepared by a process comprising: a1) oxidizing unfunctionali

What is claimed is: 1. A method comprising the steps of: a) dispersing functionalized CNTs in a solvent to form a dispersion; wherein the functionalized CNTs comprise oxidized, fluorinated CNTs; wherein the oxidized, fluorinated CNTs are prepared by a process comprising: a1) oxidizing unfunctionalized CNTs to form oxidized CNTs comprising opened ends; wherein the opened ends comprise carboxylic acid groups; and a2) fluorinating the oxidized CNTs to form the oxidized, fluorinated CNTs; wherein the fluorinating step is conducted after the oxidizing step; and wherein the fluorinating step comprises attaching fluorine moieties to sidewalls of the oxidized CNTs; b) adding an epoxy resin to the dispersion to form a mixture; c) removing the solvent from the mixture to form a substantially solvent-free mixture; d) adding a curing agent to the substantially solvent-free mixture; and e) curing the substantially solvent-free mixture to form a CNT-epoxy composite; wherein the functionalized CNTs are dispersed and integrated in the CNT-epoxy composite. 2. The method of claim 1, wherein the dispersing step comprises ultrasonication. 3. The method of claim 1, wherein the solvent is selected from the group consisting of aqueous solvents, non-aqueous solvents, and combinations thereof. 4. The method of claim 1, wherein the epoxy resin is selected from the group consisting of DGEBA, Novolac epoxy, cycloaliphatic epoxy, brominated epoxy, and combinations thereof. 5. The method of claim 1, wherein the step of adding an epoxy resin comprises a mixing of the dispersion and the epoxy resin. 6. The method of claim 5, wherein the mixing is conducted with a high-shear mixer. 7. The method of claim 1, wherein the removing step comprises heating in vacuum. 8. The method of claim 1, wherein the curing agent is selected from the group consisting of cycloaliphatic amines, aliphatic amines, aromatic amines, and combinations thereof. 9. The method of claim 1, wherein the step of adding a curing agent comprises a mixing of the curing agent and the substantially solvent-free mixture. 10. The method of claim 1, wherein the unfunctionalized CNTs comprise SWNTs. 11. The method of claim 1, wherein the CNT-epoxy composite possesses at least one enhanced property selected from the group consisting of mechanical properties, thermal properties, electrical properties, and combinations thereof; and wherein the at least one enhanced property is measured relative to a native epoxy not comprising CNTs. 12. The method of claim 11, wherein the at least one enhanced mechanical property is selected from the group consisting of an increase in Young's modulus, an increase in tensile strength, an enhanced elongation-to-break, an enhanced load transfer to the functionalized CNTs, and combinations thereof. 13. The method of claim 1, wherein the unfunctionalized CNTs comprise a carbon nanotube type selected from the group consisting of single-wall carbon nanotubes, multi-wall carbon nanotubes, double-wall carbon nanotubes, fullerene tubes, Buckytubes, graphite fibrils, and combinations thereof. 14. The method of claim 1, further comprising purifying the unfunctionalized CNTs before the oxidizing step. 15. The method of claim 1, further comprising sorting the unfunctionalized CNTs by a property; wherein the property is selected from the group consisting of length, diameter, chirality, conductivity, and combinations thereof; and wherein the sorting step takes place before the oxidizing step. 16. The method of claim 1 further comprising reacting the oxidized, fluorinated CNTs with at least one diamine to form oxidized, amino-functionalized CNTs; wherein the at least one diamine comprises a first amino group and a second amino group; wherein the step of reacting comprises displacing the fluorine moieties and bonding first amino groups of the at least one diamine to sidewalls of the oxidized, fluorinated CNTs; and wherein second amino groups of the at least one diamine are not bonded to sidewalls of the oxidized, fluorinated CNTs. 17. The method of claim 1, wherein the oxidized, amino-functionalized CNTs integrate into the CNT-epoxy composite during the curing step; wherein the at least one diamine comprises the curing agent; and wherein integration comprises a reaction of second amino groups of the at least one diamine with epoxide groups of the epoxy resin. 18. The method of claim 1, wherein the oxidized, fluorinated CNTs integrate into the CNT-epoxy composite during the curing step; wherein integration comprises forming ester linkages between the oxidized, fluorinated CNTs and the epoxy resin; wherein the ester linkages are formed by a reaction between the carboxylic acid groups and epoxide groups of the epoxy resin. 19. A method comprising the steps of: a) dispersing functionalized CNTs in a first solvent to form a dispersion of functionalized CNTs; wherein the functionalized CNTs comprise sidewall carboxylic acid-functionalized CNTs; wherein the sidewall carboxylic acid-functionalized CNTs are prepared by a process comprising: a1) dispersing unfunctionalized CNTs in a second solvent to form a dispersion of unfunctionalized CNTs; a2) adding an organic acyl peroxide of a dicarboxylic acid to the dispersion of unfunctionalized CNTs to form a reaction mixture; and a3) heating the reaction mixture to form free radicals; wherein the free radicals are of the type HO(O)C--(CH2)n.; and wherein the free radicals react with sidewalls of the unfunctionalized CNTs to form the sidewall carboxylic acid-functionalized CNTs; b) adding an epoxy resin to the dispersion of functionalized CNTs to form an epoxy mixture; c) removing the first solvent from the epoxy mixture to form a substantially solvent-free mixture; d) adding a curing agent to the substantially solvent-free mixture; and e) curing the substantially solvent-free mixture to form a CNT-epoxy composite; wherein the functionalized CNTs are dispersed and integrated in the CNT-epoxy composite. 20. The method of claim 19, wherein the unfunctionalized CNTs comprise a carbon nanotube type selected from the group consisting of single-wall carbon nanotubes, multi-wall carbon nanotubes, double-wall carbon nanotubes, fullerene tubes, Buckytubes, graphite fibrils, and combinations thereof. 21. The method of claim 19, further comprising purifying the unfunctionalized CNTs before step a1. 22. The method of claim 19, further comprising sorting the unfunctionalized CNTs by a property; wherein the property is selected from the group consisting of length, diameter, chirality, conductivity and combinations thereof; and wherein the sorting step takes place before step a1. 23. The method of claim 19, wherein the organic acyl peroxide of the dicarboxylic acid is selected from the group consisting of succinic acid peroxide, glutaric acid peroxide, and combinations thereof. 24. The method of claim 19, further comprising reacting the sidewall carboxylic acid-functionalized CNTs with a chlorinating agent to form sidewall acyl chioride-functionalized CNTs. 25. The method of claim 24, wherein the chlorinating agent is selected from the group consisting of Cl2, SOCl2, and combinations thereof. 26. The method of claim 24, further comprising reacting the sidewall acyl chloride-functionalized CNTs with a diamine to form amino-functionalized CNTs; wherein the diamine comprises a first amino group and a second amino group; wherein reacting the sidewall acyl chloride-functionalized CNTs with the diamine comprises bonding first amino groups of the diamine with the sidewall acyl chloride-functionalized CNTs to form amides; and wherein the amides are terminated with second amino groups of the diamine. 27. The method of claim 26, wherein the amino-functionalized CNTs are-integrated into the CNT-epoxy composite during the curing step; wherein integration comprises a reaction of second amino groups of the diamine with epoxide groups of the epoxy resin. 28. The method of claim 24, wherein the sidewall acyl chloride-functionalized CNTs are-integrated into the CNT-epoxy composite during the curing step; wherein the curing agent comprises a diamine; wherein the diamine comprises a first amino group and a second amino group; and wherein integration comprises a first reaction of first amino groups of the diamine with the sidewall acyl chloride-functionalized CNTs to form amides and a second reaction of second amino groups of the diamine with epoxide groups of the epoxy resin. 29. The method of claim 19, wherein the sidewall carboxylic acid-functionalized CNTs integrate into the CNT-epoxy composite during the curing step; wherein integration comprises forming ester linkages between the sidewall carboxylic acid-functionalized CNTs and the epoxy resin; wherein the ester linkages are formed by a reaction between the carboxylic acid groups and epoxide groups of the epoxy resin. 30. A method comprising the steps of: a) dispersing functionalized CNTs in a first solvent to form a dispersion of functionalized CNTs; wherein the functionalized CNTs comprise fluorinated, hydroxyl-functionalized CNTs; wherein the fluorinated, hydroxyl-functionalized CNTs are prepared by a process comprising: a1) reacting unfunctionalized CNTs with fluorine to form fluorinated CNTs; a2) dispersing the fluorinated CNTs in a second solvent to form a dispersion of fluorinated CNTs; a3) reacting a dialcohol with a metal hydroxide to form a metal salt of the dialcohol; and a4) reacting the metal salt of the dialcohol with the fluorinated CNTs to form the fluorinated, hydroxyl-functionalized CNTs; b) adding an epoxy resin to the dispersion of functionalized CNTs to form a mixture; c) removing the first solvent from the mixture to form a substantially solvent-free mixture; d) adding a curing agent to the substantially solvent-free mixture; and e) curing the substantially solvent-free mixture to form a CNT-epoxy composite; wherein the functionalized CNTs are dispersed and integrated in the CNT-epoxy composite. 31. The method of claim 30, further comprising reacting the fluorinated, hydroxyl-functionalized CNTs with epichiorohydrin to form flourinated, epoxide-functionalized CNTs. 32. The method of claim 31, wherein the fluorinated, epoxide-functionalized CNTs integrated into the CNT-epoxy composite during the curing step; wherein the curing agent comprises at least one amine; and wherein integration comprises a reaction between the at least one amine comprising the curing agent and epoxide groups comprising the fluorinated, epoxide-functionalized CNTs. 33. The method of claim 30, wherein the unfunctionalized CNTs comprise a carbon nanotube type selected from the group consisting of single-wall carbon nanotubes, multi-wall carbon nanotubes, double-wall carbon nanotubes, fullerene tubes, Buckytubes, graphite fibrils, and combinations thereof. 34. The method of claim 30, further comprising purifying the unfunctionalized CNTs before step a1. 35. The method of claim 30, further comprising sorting the unfunctionalized CNTs by a property; wherein the property is selected from the group consisting of length, diameter, chirality, conductivity, and combinations thereof; and wherein the sorting step takes place before the oxidizing step. 36. The method of claim 30, wherein the dialcohol comprises bisphenol-A. 37. The method of claim 30, wherein the metal hydroxide is selected from the group consisting of LiOH, NaOH, KOH, and combinations thereof. 38. A CNT-epoxy polymer composite prepared by a process comprising the steps of: a) dispersing functionalized CNTs in a solvent to form a dispersion; wherein the functionalized CNTs comprise oxidized, fluorinated CNTs; wherein the oxidized, fluorinated CNTs are prepared by a process comprising: a1) oxidizing unfunctionalized CNTs to form oxidized CNTs comprising opened ends; wherein the opened ends comprise carboxylic acid groups; and a2) fluorinating the oxidized CNTs to form the oxidized, fluorinated CNTs; wherein the fluorinating step is conducted after the oxidizing step; and wherein the fluorinating step comprises attaching fluorine moieties to sidewalls of the oxidized CNTs; b) adding an epoxy resin to the dispersion to form a mixture; c) removing the solvent from the mixture to form a substantially solvent-free mixture; d) adding a curing agent to the substantially solvent-free mixture; and e) curing the substantially solvent-free mixture to form the CNT-epoxy polymer composite; wherein the functionalized CNTs are dispersed and integrated in the CNT-epoxy polymer composite. 39. The CNT-epoxy polymer composite prepared by the process of claim 38, wherein the dispersing step comprises ultrasonication. 40. The CNT-epoxy polymer composite prepared by the process of claim 38, wherein the solvent is selected from the group consisting of aqueous solvents, non-aqueous solvents, and combinations thereof. 41. The CNT-epoxy polymer composite prepared by the process of claim 38, wherein the epoxy resin is selected from the group consisting of DGEBA, Novolac epoxy, cycloaliphatic epoxy, brominated epoxy, and combinations thereof. 42. The CNT-epoxy polymer composite prepared by the process of claim 38, wherein the step of adding an epoxy resin comprises a mixing of the dispersion and the epoxy resin. 43. The CNT-epoxy polymer composite prepared by the process of claim 42, wherein the mixing is conducted with a high-shear mixer. 44. The CNT-epoxy polymer composite prepared by the process of claim 38, wherein the removing syep comprises heating in vacuum. 45. The CNT-epoxy polymer composite prepared by the process of claim 38, wherein the curing agent is selected from the group consisting of cycloaliphatic amines, aliphatic amines, aromatic amines, and combinations thereof. 46. The CNT-epoxy polymer composite prepared by the process of claim 38, wherein the step of adding a curing agent comprises a mixing of the curing agent and the substantially solvent-free mixture. 47. The CNT-epoxy polymer composite prepared by the process of claim 38, wherein the functionalized CNTs comprise SWNTs. 48. The CNT-epoxy polymer composite prepared by the process of claim 38, wherein the CNT-epoxy polymer composite possesses at least one enhanced mechanical property; wherein the at least one enhanced mechanical property is measured relative to a native epoxy not comprising CNTs. 49. The CNT-epoxy polymer composite prepared by the process of claim 48, wherein the at least one enhanced mechanical property is selected from the group consisting of an increase in Young's modulus, an increase in tensile strength, an enhanced elongation-to-break, an enhanced load transfer to the functionalized CNTs, and combinations thereof. 50. The CNT-epoxy polymer composite prepared by the process of claim 38, wherein the unfunctionalized CNTs comprise a carbon nanotube type selected from the group consisting of single-wall carbon nanotubes, multi-wall carbon nanotubes, double-wall carbon nanotubes, fullerene tubes, Buckytubes, graphite fibrils, and combinations thereof. 51. The CNT-epoxy polymer composite prepared by the process of claim 38, wherein the process further comprises reacting the oxidized, fluorinated CNTs with at least one diamine to form oxidized, amino-functionalized CNTs; wherein the at least one diamine comprises a first amino group and a second amino group; wherein the step of reacting comprises displacing the fluorine moieties and bonding first amino groups of the at least one diamine to sidewalls of the oxidized, fluorinated CNTs; and wherein second amino groups of the at least one diamine are not bonded to sidewalls of the oxidized, fluorinated CNTs. 52. The CNT-epoxy polymer composite prepared by the process of claim 51, wherein the oxidized, fluorinated CNTs integrate into the CNT-epoxy polymer composite during the curing step; wherein the at least one diamine comprises the curing agent; wherein the at least one diamine comprises a first amino group and a second amino group; and wherein integration comprises a reaction of second amino groups of the at least one diamine with epoxide groups of the epoxy resin. 53. The CNT-epoxy polymer composite prepared by the process of claim 38, wherein the oxidized, fluorinated CNTs integrate into the CNT-epoxy polymer composite during the curing step; and wherein integration comprises-by forming ester linkages between the oxidized, fluorinated CNTs and the epoxy resin; wherein the ester linkages are formed by a reaction between the carboxylic acid groups and epoxide groups of the epoxy resin. 54. The CNT-epoxy polymer composite prepared by the process of claim 38, further comprising at least one additive selected from the group consisting of inhibitors, curing agents, viscosity modifiers, anti-degradation species, colorants, nanoparticles, nanoclays, and combinations thereof. 55. The CNT-epoxy polymer composite prepared by the process of claim 38, further comprising a fiber reinforcement selected from the group consisting of fiberglass, carbon fiber, graphite fabric, KEVLAR, and combinations thereof. 56. A CNT-epoxy polymer composite prepared by a process comprising the steps of: a) dispersing functionalized CNTs in a first solvent to form a dispersion of functionalized CNTs; wherein the functionalized CNTs comprise sidewall carboxylic acid-functionalized CNTs; wherein the sidewall carboxylic acid-functionalized CNTs are prepared by a process comprising: a1) dispersing unfunctionalized CNTs in a second solvent to form a dispersion of unfunctionalized CNTs; a2) adding an organic acyl peroxide of a dicarboxylic acid to the dispersion of unfunctionalized CNTs to form a reaction mixture; and a3) heating the reaction mixture to form free radicals; wherein the free radicals are of the type HO(O)C--(CH2)n.; and wherein the free radicals react with sidewalls of the unfunctionalized CNTs to form the sidewall carboxylic acid-functionalized CNTs; b) adding an epoxy resin to the dispersion of functionalized CNTs to form an epoxy mixture; c) removing the first solvent from the epoxy mixture to form a substantially solvent-free mixture; d) adding a curing agent to the substantially solvent-free mixture; and e) curing the substantially solvent-free mixture to form the CNT-epoxy polymer composite; wherein the functionalized CNTs are dispersed and integrated in the CNT-epoxy polymer composite. 57. The CNT-epoxy polymer composite prepared by the process of claim 56, wherein the unfunctionalized CNTs comprise a carbon nanotube type selected from the group consisting of single-wall carbon nanotubes, multi-wall carbon nanotubes, double-wall carbon nanotubes, fullerene tubes, Buckytubes, graphite fibrils, and combinations thereof. 58. The CNT-epoxy polymer composite prepared by the process of claim 56, wherein the process further comprises reacting the sidewall carboxylic acid-functionalized CNTs with a chlorinating agent to form sidewall acyl chioride-functionalized CNTs. 59. The CNT-epoxy polymer composite prepared by the process of claim 58, wherein the process further comprises reacting the sidewall acyl chloride-functionalized CNTs with a diamine to form amino-functionalized CNTs; wherein the diamine comprises a first amino group and a second amino group; wherein reacting the sidewall acyl chloride-functionalized CNTs with the diamine comprises bonding first amino groups of the diamine with the sidewall acyl chloride-CNTs to form amides; and wherein the amides are terminated with second amino groups of the diamine. 60. The CNT-epoxy polymer composite prepared by the process of claim 59, wherein the amino-functionalized CNTs are-integrated into the CNT-epoxy polymer composite during the curing step; wherein integration comprises a reaction of second amino groups of the diamine with epoxide groups of the epoxy resin. 61. The CNT-epoxy polymer composite prepared by the process of claim 58, wherein the sidewall acyl chloride-functionalized CNTs are-integrated into the CNT-epoxy polymer composite during the curing step; wherein the curing agent comprises a diamine; wherein the diamine comprises a first amino group and a second amino group; and wherein integration comprises a first reaction of first amino groups of the diamine with the sidewall acyl chloride-functionalized CNTs to form amides and a second reaction of second amino groups of the diamine with epoxide groups of the epoxy resin. 62. The CNT-epoxy polymer composite prepared by the process of claim 56, wherein the sidewall carboxylic acid-functionalized CNTs integrate into the CNT-epoxy polymer composite during the curing step; wherein integration comprises forming ester linkages between the sidewall carboxylic acid-functionalized CNTs and the epoxy resin; wherein the ester linkages are formed by a reaction between the carboxylic acid groups and epoxide groups of the epoxy resin. 63. The CNT-epoxy polymer composite prepared by the process of claim 56, further comprising at least one additive selected from the group consisting of inhibitors, curing agents, viscosity modifiers, anti-degradation species, colorants, nanoparticles, nanoclays, and combinations thereof. 64. The CNT-epoxy polymer composite prepared by the process of claim 56, further comprising a fiber reinforcement selected from the group consisting of fiberglass, carbon fiber, graphite fabric, KEVLAR, and combinations thereof. 65. A CNT-epoxy polymer composite prepared by a process comprising the steps of: a) dispersing functionalized CNTs in a first solvent to form a dispersion of functionalized CNTs; wherein the functionalized CNTs comprise fluorinated, hydroxyl-functionalized CNTs; wherein the fluorinated, hydroxyl-functionalized CNTs are prepared by a process comprising: a1) reacting unfunctionalized CNTs with fluorine to form fluorinated CNTs; a2) dispersing the fluorinated CNTs in a second solvent to form a dispersion of fluorinated CNTs; a3) reacting a dialcohol with a metal hydroxide to form a metal salt of the dialcohol; and a4) reacting the metal salt of the dialcohol with the fluorinated CNTs to form the fluorinated, hydroxyl-functionalized CNTs; b) adding an epoxy resin to the dispersion of functionalized CNTs to form a mixtures; c) removing the first solvent from the mixture to form a substantially solvent-free mixture; d) adding a curing agent to the substantially solvent-free mixture; and e) curing the substantially solvent-free mixture to form the CNT-epoxy polymer composite; wherein the functionalized CNTs are dispersed and integrated in the CNT-epoxy polymer composite. 66. The CNT-epoxy polymer composite prepared by the process of claim 65, wherein the process further comprises reacting the fluorinated, hydroxyl-functionalized CNTs with epichlorohydrin to form fluorinated, epoxide-functionalized CNTs. 67. The CNT-epoxy polymer composite prepared by the process of claim 66, wherein the fluorinated, epoxide-functionalized CNTs are integrated into the CNT-epoxy polymer composite during the curing step; wherein the curing agent comprises at least one amine; and wherein integration comprises a reaction between the at least one amine comprising the curing agent and epoxide groups comprising the fluorinated, epoxide-functionalized CNTs. 68. The CNT-epoxy polymer composite prepared by the process of claim 65, wherein the unfunctionalized CNTs comprise a carbon nanotube type selected from the group consisting of single-wall carbon nanotubes, multi-wall carbon nanotubes, double-wall carbon nanotubes, fullerene tubes, Buckytubes, graphite fibrils, and combinations thereof. 69. The CNT-epoxy polymer composite prepared by the process of claim 65, wherein the dialcohol comprises bisphenol-A. 70. The CNT-epoxy polymer composite prepared by the process of claim 65, further comprising at least one additive selected from the group consisting of inhibitors, curing agents, viscosity modifiers, anti-degradation species, colorants, nanoparticles, nanoclays, and combinations thereof. 71. The CNT-epoxy polymer composite prepared by the process of claim 65, further comprising a fiber reinforcement selected from the group consisting of fiberglass, carbon fiber, graphite fabric, KEVLAR, and combinations thereof.