News Column

Patent Application Titled "Highly Soluble Carbon Nanotubes with Enhanced Conductivity" Published Online

June 12, 2014



By a News Reporter-Staff News Editor at Politics & Government Week -- According to news reporting originating from Washington, D.C., by VerticalNews journalists, a patent application by the inventors Landorf, Christopher (Springfield, MO); Jones, Carissa (Springfield, MO); Nelson, Marriana (Springfield, MO), filed on January 25, 2014, was made available online on May 29, 2014.

The assignee for this patent application is Brewer Science Inc.

Reporters obtained the following quote from the background information supplied by the inventors: "The present invention is concerned with noncovalently functionalizing carbon nanotubes using strong acids and functionalized polyaromatic molecules in order to increase their solubilities and/or conductivities.

"Carbon nanotubes (CNTs) have shown great promise for conductive trace applications, especially in printed electronics. Printed CNT traces offer a number of benefits over traditional metal traces, including ease of application and of mechanical flexibility. However, 'raw' CNTs are usually produced in a very disordered and impure powder, and must be purified and dispersed to create the conductive (or semiconductive) 'inks' used to print the CNT traces. Getting CNTs to remain dispersed in solution, however, can be a challenge. CNTs very strongly attract each other due to van der Waals forces, causing them to agglomerate and fall out of solution. In order to create useful CNT inks for printing, processes must be developed to ensure that the CNTs remain dispersed.

"Several methods have been used to make carbon nanotubes (CNTs) more dispersible, including oxidation processes, the use of surfactants, covalent functionalization with solubilizing groups, and non-covalent functionalization. Of these methods, non-covalent functionalization has the least effect on the electronic properties of the carbon nanotubes. Covalent functionalization creates defects in the pi network of the CNTs, which adversely affects their conductivity. Similarly, oxidation of the nanotubes will negatively affect the electronic characteristics of the CNTs, as the oxidation damages the tubes and could decrease their size. The addition of additives to the solution, such as surfactants, can also disrupt the electronic properties of the final ink-printed CNT films. To reduce this effect, post-applications treatments, including repeated washings, of the printed CNT films are necessary, which creates extra steps, yield lost, and large amounts of waste, and still may not restore the conductivity of the original CNTs.

"Several methods of non-covalently functionalizing carbon nanotubes have been published. If the functional group is a liquid, then simply stirring at a raised temperature can be effective. Some solids can be melted with the carbon nanotubes but many solids decompose before melting, which is particularly the case for many polyaromatic hydrocarbons. Sonication can also be used to temporarily disperse CNTs in a solvent. Sonication can be used in conjunction with another functionalizing method, since it temporarily breaks up the carbon nanotube bundles and allows the functionalizing groups to get between the CNTs. However, strong or prolonged sonication has a tendency to damage carbon nanotubes, which likely results in less than desirable electronic properties.

"There is a need for improved methods of solubilizing carbon nanotubes while preserving, and even enhancing, their conductivity."

In addition to obtaining background information on this patent application, VerticalNews editors also obtained the inventors' summary information for this patent application: "The present invention overcomes the problems of the prior art by providing a method of preparing a carbon nanotube dispersion with improved carbon nanotube solubilities and conductivities. The method comprises providing a mixture of carbon nanotubes, a compound comprising at least one polyaromatic moiety, and an acid. The compound comprising at least one polyaromatic moiety is noncovalently bonded with the carbon nanotubes, and the acid is reacted with the at least one polyaromatic moiety. The invention is also directed towards the dispersion formed by this method.

"In another embodiment, the invention provides a dispersion comprising carbon nanotubes noncovalently bonded to compounds comprising respective polyaromatic moieties. At least some of the polyaromatic moieties are reacted with an acid. The dispersion has a carbon nanotube concentration of at least about 0.05% by weight, based upon the total weight of the dispersion taken as 100% by weight. The dispersion is also formable into a film having a sheet resistance of less than about 7,000 SI/sq.

BRIEF DESCRIPTION OF THE DRAWINGS

"FIG. 1 is a graph depicting the D/G ratio of the sample prepared in Example 1;

"FIG. 2 is a graph showing the TGA analysis of the sample prepared in Example 1;

"FIG. 3 is a graph of the TGA analysis of raw CG200 carbon nanotubes;

"FIG. 4 is a graph depicting the D/G ratio of the sample prepared in Example 2;

"FIG. 5 is a graph showing the D/G ratio of raw CG200 carbon nanotubes;

"FIG. 6 is a graph illustrating the Raman spectrum of the sample prepared in Example 2;

"FIG. 7 is a graph depicting the Raman spectrum of raw CG200 carbon nanotubes;

"FIG. 8 is a graph depicting the D/G ratio of the sample prepared in Example 3;

"FIG. 9 is a graph showing the D/G ratio of raw SG65 carbon nanotubes;

"FIG. 10 is a graph illustrating the Raman spectrum of the sample prepared in Example 3;

"FIG. 11 is a graph depicting the D/G ratio of the sample prepared in Example 4;

"FIG. 12 is a graph illustrating the Raman spectrum of the sample prepared in Example 4;

"FIG. 13 is a graph depicting the D/G ratios of the sample prepared in Example 5 and of XBC3350 carbon nanotubes (for readability, the spectrum for the XBC3350 was multiplied by a factor of 0.473);

"FIG. 14 is a graph depicting the Raman spectra of the sample prepared in Example 5 and of XBC3350 carbon nanotubes (for readability, the spectrum for the XBC3350 was multiplied by a factor of 0.473);

"FIG. 15 is a graph showing the D/G ratios of the second sample prepared in Example 6 and of CG200 carbon nanotubes (for readability, the spectrum for the CG200 was multiplied by a factor of 4.212);

"FIG. 16 is a graph depicting the Raman spectra of the second sample prepared in Example 6 and of CG200 carbon nanotubes (for readability, the spectrum for the CG200 was multiplied by a factor of 4.212);

"FIG. 17 provides the NMR spectrum of the reaction product of 1-pyrenemethylamine hydrochloride with fuming sulfuric acid;

"FIG. 18 shows the mass spectrum of the reaction product of 1-pyrenemethylamine hydrochloride with fuming sulfuric acid; and

"FIG. 19 shows the chemical structure of the reaction product of 1-pyrenemethylamine hydrochloride with fuming sulfuric acid."

For more information, see this patent application: Landorf, Christopher; Jones, Carissa; Nelson, Marriana. Highly Soluble Carbon Nanotubes with Enhanced Conductivity. Filed January 25, 2014 and posted May 29, 2014. Patent URL: http://appft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&u=%2Fnetahtml%2FPTO%2Fsearch-adv.html&r=5336&p=107&f=G&l=50&d=PG01&S1=20140522.PD.&OS=PD/20140522&RS=PD/20140522

Keywords for this news article include: Chemicals, Chemistry, Fullerenes, Sulfur Acids, Nanotechnology, Sulfuric Acids, Carbon Nanotubes, Brewer Science Inc., Emerging Technologies.

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Source: Politics & Government Week


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