Chemistry of inorganic compounds – Carbon or compound thereof – Elemental carbon
Reexamination Certificate
1999-09-30
2002-04-09
Richter, Johann (Department: 1621)
Chemistry of inorganic compounds
Carbon or compound thereof
Elemental carbon
C562S509000, C564S123000
Reexamination Certificate
active
06368569
ABSTRACT:
TECHNICAL FIELD
The present invention relates to the dissolution of full length or unshortened carbon nanotubes in solutions and more particularly, to a method of dissolving naked nanotube carbon metals and semiconductors in organic solutions.
BACKGROUND OF THE INVENTION
All previous work on carbon nanotubes (both single-walled and multi-walled) has been carried out on the usual intractable, insoluble form of this material [Yakobson, B. I.; Smalley, R. E., Fullerene Nanotubes: C1,000.000 and Beyond. American Scientist 1997, 85, 324-337.] This form of the material is not amenable to many of the processing steps that are necessary if the carbon nanotubes (CNTs) are to reach their full potential—particularly in applications that require these materials in the form of polymers, copolymers, composites, ceramics and moldable forms.
While present forms of the CNTs can be heterogeneously dispersed in various media, the interactions between the CNTs and host and between the CNTs themselves are simply physical, and without the formation of chemical bonds. Thus, the advantageous properties of the CNTs are unlikely to be realized on a macroscopic level. What is needed is a method to prepare well-dispersed forms of CNTs perhaps by inducing them to exfoliate from the bundles and dissolve in organic solvents. Although long believed to be impossible, [Ebbesen, T. W., Cones and Tubes: Geometry in the Chemistry of Carbon. Acc. Chem. Res. 1998, 31, 558-566] we now teach such a procedure for the dissolution of all types of CNTs [Chen, J.; Hamon, M. A.; Hu, H.; Chen, Y.; Rao, A. M.; Eklund, P. C.; Haddon, R. C., Solution Properties of Single-Walled Carbon Nanotubes. Science 1998, 282, 95-98; Hamon, M. A.; Chen, J.; Hu, H.; Chen, Y.; Rao, A. M.; Eklund, P. C.; Haddon, R. C., Dissolution of Single-Walled Carbon Nanotubes. Adv. Mater. 1999, 11, 834-840].
SUMMARY OF THE INVENTION
Accordingly, it is a primary object of the present invention to overcome the above-described limitations and disadvantages of the prior art by providing (1) a method of solubilizing carbon nanotubes; and (2) solutions of carbon nanotubes dissolved in an organic solvent. Such solutions are anticipated to be useful in the functionalization chemistry of the open ends, the exterior walls or convex face and the interior cavity or concave face of carbon nanotubes and processing useful nanotube based polymer, copolymer and composite products and devices for a multitude of applications in various industries including aerospace, battery, fuel cell, healthcare and electromagnetic radiation shielding.
Advantageously, as a result of the present invention, functionalization chemistry of the CNTs can be determined through the study of both the ionic and covalent solution phase chemistry with concomitant modulation of the single wall nanotube band structure.
Additional objects, advantages, and other novel features of the invention will be set forth in part in the description that follows and in part will become apparent to those skilled in the art upon examination of the following or may be learned with the practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
To achieve the foregoing and other objects, and in accordance with the purposes of the present invention as described herein, a novel and improved method of dissolving CNT metals and semiconductors in common organic solutions is provided. The method comprises terminating the CNTs with carboxylic acid groups. This is followed by the attaching of an aliphatic carbon chain to the of the CNTs so as to render the CNTs soluble in the selected organic solvent.
The terminating step may be further described as the reacting of the CNTs with a mineral acid. This may be accomplished by adding a mineral acid (eg. HCl, HNO
3
, H
2
SO
4
) to an aqueous suspension of the CNTs to protonate the carboxylate groups. The attaching step includes directly reacting the carbon nanotubes with an amine having a formula RNH
2
or R
1
R
2
NH wherein R, R
1
and R
2
=(CH
2
)
n
CH
3
where n=9-50. Alternatively, the attaching step includes directly reacting the carbon nanotubes with an alkylaryl amine having a formula RNH
2
or R
1
R
2
NH wherein R, R
1
and R
2
=(C
6
H
4
)(CH
2
)
n
CH
3
where n=5-50.
In accordance with yet another alternative, the attaching step includes the steps of (a) converting the carboxylic acid groups on the carbon nanotubes to acid chloride groups by reacting the carbon nanotubes with a reagent selected from a group consisting of SOCl
2
, PCl
5
and any mixtures thereof; (b) mixing the acid chloride converted carbon nanotubes with an amine or alkylaryl amine having a formula RNH
2
or R
1
R
2
NH wherein R, R
1
and R
2
=(CH
2
)
n
CH
3
and n=9-50 or R, R
1
and R
2
=(C
6
H
4
) (CH
2
)
n
CH
3
and =5-50; and (c) heating the resulting mixture to a temperature between 50-200° C. More preferably, the heating step is to 90-100° C. for at least 96 hours.
The method may also be described as including the further step of dissolving the resulting carbon nanotubes in the selected organic solvent. That organic solvent is preferably an aromatic or chlorinated solvent. Solvents in which the CNTs of the present invention may be solubilized include but are not limited to chloroform, dichloromethane, benzene, toluene, chlorobenzene, 1,2-dichlorobenzene, dichlorocarbonbenzene, ether, tetrahydrofuran and mixtures thereof.
Advantageously, such a solution not only allows the study of the functionalization chemistry of the open ends, the exterior walls or convex face and the interior cavity or concave face of the nanotubes, but also processing of the nanotubes into useful products for various applications including as intermediates in the preparation of polymer, copolymer and composite materials.
Still other objects of the present invention will become apparent to those skilled in this art from the following description wherein there is shown and described a preferred embodiment of this invention, simply by way of illustration of one of the modes and alternate embodiments best suited to carry out the invention. As it will be realized, the invention is capable of still other and different embodiments, and its several details are capable of modifications in various, obvious aspects all without departing from the invention. Accordingly, the drawings and descriptions will be regarded as illustrative in nature and not as restrictive.
DETAILED DESCRIPTION OF THE INVENTION
In the novel method of the present invention, we begin with raw, as prepared, CNT soot (AP-CNTs). The AP-CNTs come in two basic forms: AP-single-walled carbon nanotubes (AP-SWNTs) available from CarboLex, Inc. of Lexington, Kentucky and AP-multi-walled carbon nanotubes (AP-MWNTs) available from MER Corporation of 7960 South Kolb Rd, Tucson, Ariz. 85706. The AP-SWNTs are prepared by use of an electric arc technique similar to that described by Journet, C.; Maser, W. K.; Bernier, P.; Loiseau, A.; Lamy de la Chappelle, M.; Lefrant, S.; Deniard, P.; Lee, R. and Fischer, J. E., in Large Scale Production of Single-Walled Carbon Nanotubes by the Electric-Arc Technique. Nature 1997 388, 756-758. The estimated purity of this material is 40-60% SWNT by volume. Batches of 10 grams may be prepared in a single run and there is considerable scope for further increase in scale. Thus it is possible to contemplate the very large-scale production of this material in the future. The AP-MWNTs are of an estimated purity of less than 10% and the nanotubes are of poor quality with many defective and fused together. We describe herein routes to soluble CNTs, starting from AP-SWNTs and AP-MWNTs.
In accordance with the present invention, full length or unshortened carbon nanotubes are solubilized. This is accomplished utilizing a simple procedure which advantageously preserves the length of the carbon nanotubes which is one of their primary att
Chen Jian
Haddon Robert C.
Hamon Mark A.
King & Schickli PLLC
Parsa J.
Richter Johann
University of Kentucky Research Foundation
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