CN1309887C - Process for derivatizing carbon nanotubes with diazonium species and compositions thereof - Google Patents

Abstract

The invention incorporates new processes for the chemical modification of carbon nanotubes. Such processes involve the derivatization of multi- and single-wall carbon nanotubes, including small diameter (ca. 0.7 nm) single-wall carbon nanotubes, with diazonium species. The method allows the chemical attachment of a variety of organic compounds to the side and ends of carbon nanotubes. These chemically modified nanotubes have applications in polymer composite materials, molecular electronic applications, and sensor devices. The methods of derivatization include electrochemical induced reactions, thermally induced reactions (via in-situ generation of diazonium compounds or pre-formed diazonium compounds), and photochemically induced reactions. The derivatization causes significant changes in the spectroscopic properties of the nanotubes. The estimated degree of functionality is ca. 1 out of every 20 to 30 carbons in a nanotube bearing a functionality moiety. Such electrochemical reduction processes can be adapted to apply site-selective chemical functionalization of nanotubes. Moreover, when modified with suitable chemical groups, the derivatized nanotubes are chemically compatible with a polymer matrix, allowing transfer of the properties of the nanotubes (such as, mechanical strength or electrical conductivity) to the properties of the composite material as a whole. Furthermore, when modified with suitable chemical groups, the groups can be polymerized to form a polymer that includes carbon nanotubes.

Description

Derivative method and product of carbon nanotube and its sidewall, single-layer nanotube solution, method for preparing polymer material and polymer material

The present invention was made in connection with research under Grant No. NASA-JSC-NCC 9-77 of the National Aeronautics and Space Administration, Grant No. NSR-DMR-0073046 of the National Science Foundation, and Grant No. NO0014-99-1-0406 of DARPA/ONR related.

field of invention

The present invention generally relates to carbon nanotubes. More specifically, the present invention relates to carbon nanotubes derivatized with diazo compounds, and uses of the derivatized carbon nanotubes.

Background of the invention

Fullerenes are closed cage molecules composed entirely of ^SP2 hybridized carbons arranged in hexagonal and pentagonal shapes. Fullerenes (such as C ₆₀ ) were initially regarded as closed spherical cages condensed from carbon vapor. Fullerene tubes are generated by preparing spherical fullerenes from carbon vapor by carbon arc method to deposit carbon on the cathode (Ebbesen et al. (Ebbesen I), "Large-Scale Synthesis of Carbon Nanotubes", Nature, Vol.358, P220 (July 16, 1992) and Ebbesen et al. (Ebbesen II), "Carbon Nanotubes", Amual Review of Materials Science, Vol. 24, P235 (1994)). The tubes mentioned here refer to carbon nanotubes. Many of the carbon nanotubes produced by these methods are multilayered nanotubes, that is, the carbon nanotubes resemble coaxial cylinders. Carbon nanotubes with up to seven layers have been described in the prior art (Ebbesen, Li jima et al., "Helical graphitic carbon microtubes", Nature, Vol. 354, P56 (November 7, 1991)).

Since 1991, great attention has been paid to carbon nanotubes, especially single-walled carbon nanotubes, to facilitate their handling, to improve the solubility of such nanotubes, and to make nanotubes easier to form composites, etc. That's because single-walled carbon nanotubes are one of the more astonishing discoveries in chemistry and materials science in recent years. Nanotubes have extremely strong strength, extraordinary length-to-diameter ratio, and are also excellent thermal and electrical conductors. Much speculation has been made about its potential applications, and some progress is being made toward commercial application. Therefore, in certain applications, it is necessary to chemically modify single-walled carbon nanotubes, as well as multi-walled carbon nanotubes. For example, such applications require the grafting of certain moieties to nanotubes; allow modified nanotubes, such as single-walled carbon nanotubes, to be assembled on the surface of electronic devices; allow reactions with the host of composite materials; allow various Various functional groups are attached to nanotubes such as single-walled carbon nanotubes for sensing applications.

There have been many research reports and reviews on the preparation and physical properties of carbon nanotubes, and research reports on the chemical manipulation of nanotubes have gradually emerged. There have been reports (Rao et al., Chem.Commun., 1996, 1525-1525; Wong et al., Nature, 1998, 394:52-55,) for carboxyl groups to functionalize the ends of nanotubes, followed by further manipulation via thiol linkage onto gold particles (Liu et al., Sicence, 1998, 280:1253-1256). Haddon and his collaborators (Chen et al., Science, 1998, 282:95-98) reported that by adding octadecylamine groups to the nanotube ports, dichlorocarbene was added to the side walls, even in relatively small amounts ( ~2%) to produce solvated single-walled carbon nanotubes.

The range of successful covalent derivatization reactions on the sidewalls of single-walled carbon nanotubes is limited, and the reactivity of the sidewalls is similar to that of the graphite basal plane (Aihara, J, J. Phys. Chem. 1994, 98, 9773-9776) . A feasible method to directly functionalize the sidewall of single-walled carbon nanotubes is the fluorination reaction at high temperature. This approach has been described in U.S. Patent Application Serial No. 09/810,390, "Chemical Derivatization of Facilitated Solvation of Single-Walled Carbon Nanotubes, and Formation of Catalyst-Containing Seed Materials for Carbon Fiber Fabrication" by Margraves et al., filed March 16, 2001. Disclosed in Applications of Derivative Nanotubes of , a co-pending application commonly assigned to the assignee of that application. These functionalized nanotubes are defluorinated either by hydrazine treatment or by reaction with strong nucleophiles such as alkyllithium. While fluorinated nanotubes offer excellent utilization of various functionalized materials, their two-step protocol and functional organolithium make such methods incompatible with certain carbon nanotube end uses. Other attempts at sidewall modification have also been made, all hampered by the presence of large amounts of graphite or amorphous carbon impurities. (Chen, Y et al., J. Mater. Res. 1998 13, 2423-2431).

Therefore, there is a need to develop a straightforward method (ie, a one-step process and compatible with certain nanotube end uses) of highly functionalized nanotubes that can be tuned. Such applications include taking advantage of nanotubes' extreme strength, exceptional length-to-diameter ratio, and excellent thermal and electrical conductivity.

Therefore, the object of the present invention is to provide a derivation method of carbon nanotubes, especially a derivation method of sidewalls and end caps of single-layer carbon nanotubes. The chemistry used is straightforward, tuned and compatible with the end use and application of the nanotubes.

Summary of the invention

The present invention specifically describes a new method for chemical modification of carbon nanotubes. Such methods involve the derivatization of multiwalled and single-walled carbon nanotubes, including small-diameter (about 0.7 nm) single-walled carbon nanotubes derivatized with diazo compounds. This method allows a wide variety of organic compounds to be chemically attached to the sidewalls and ports of carbon nanotubes. Such chemically modified carbon nanotubes are used in polymer composites, molecular electronics and sensor elements. Derivatization includes electrochemically induced reactions, thermally induced reactions (by in situ or pre-generated diazo compounds) and photochemically induced reactions. Derivatization significantly changes the spectral properties of the nanotubes. The functionality is estimated to be approximately one functional moiety for every 20-30 carbon atoms in the nanotube.

The electrochemical induction method involves the use of nanotube assembly steps, such as a piece of "Bucky paper" (bucky paper) or mat, which can be held by spring clips covered with silver paste, immersed in acetonitrile solution of diazonium salt and supporting dielectric salt. A potential (typically a negative potential) is applied to the nanotube assembly. By such a method, molecular wires (such as oligo(phenyleneethynylene) molecular wires) and molecular electronic components are covalently linked to the nanotubes. It represents the combination of linear nanotubes with molecular wires, and with molecular electronic components.

This electrochemical method can be used for site-selective chemical functionalization of nanotubes. Also, it facilitates the controlled attachment of two or more different chemical functional groups to different parts of the nanotube.

The thermal induction method includes the steps of treating a dispersion of carbon nanotubes in an organic solvent mixture with a precursor of an active diazo compound. The precursor is then converted in situ into an active diazonium compound whose thermal decomposition leads to chemical attachment to the carbon nanotubes. Such a method is believed to have the scalability advantage of eliminating the need to separate and preserve potentially labile diazonium compounds, components that can react with carbon nanotubes.

Furthermore, the heat-induced method also includes a step using a preformed diazo compound. The reactants were previously prepared, separated and added to the mixture. Thus, additional variables include the temperature of the process (ambient, higher and lower), the ratio of reactants, and the type of organic solvent.

The photochemical induction method is similar to the thermochemical induction reaction, except that the photochemical method (instead of thermal induction) is used to decompose the diazo compound, resulting in some parts being chemically attached to the carbon nanotubes.

After modification with appropriate chemical groups, the nanotubes are chemically compatible with the polymer matrix, enabling the substantial conversion of nanotube properties (eg, mechanical strength) into composite properties. For this purpose, the modified carbon nanotubes can be intimately mixed with the polymer material (physical blending), and/or, if desired, allowed to react at room temperature or higher. These methods can be used to attach functional groups to nanotubes, which can be further covalently bonded to the polymer matrix or directly bonded between two nanotubes.

There are a wide variety of chemical structures of the polymer matrix, such as polyethylene, various epoxy resins, polypropylene, polycarbonate, etc. In general, possible composite materials can be made of chemically modified nanotubes with thermoplastics, thermosets, elastomers, etc. A wide variety of possible chemical functional groups can also be attached to the nanotubes. Specific functional groups are selected to enhance compatibility with the particular polymer matrix desired and, if desired, can result in chemical bonding to the host material.

Moreover, nanotubes, after modification with appropriate chemical functional groups, can be used as generators of polymer growth, i.e., nanotubes derived from functional groups can be active moieties in polymerization processes that form chemically Composite materials containing carbon nanotubes.

Brief description of the drawings

Figure 1 shows the structures of some aryldiazonium salts used in the derivatization reactions of single-walled carbon nanotubes.

Figure 2 shows the scheme employed for the preparation of Compound 9 and Compound 11 identified in Figure 1 .

Figure 3 shows the absorption spectra in dimethylformamide, (a) for SWNT-p and (b) for SWNT-1.

Figure 4 shows the absorption spectra in dimethylformamide, (a) for SWNT-p and (b) for SWNT-8.

Figure 5 shows the Raman spectra of solid samples excited at 782nm, (a) for SWNT-p and (b) for SWNT-1.

Figure 6 shows the Raman spectra of the radial breathing mode region (a) for SWNT-4 and (b) for SWNT-p.

Figure 7 shows the infrared spectra (attenuated total reflection) of derivatized nanotubes, (a) for SWNT-4 and (b) for SWNT-6.

Figure 8 shows the thermogravimetric analysis data of SWNT-10 in argon.

Figure 9 shows the Raman spectra, (a) for SWNT-p, (b) for SWNT-2 and (c) for SWNT-2 after thermogravimetric analysis.

Figure 10 shows high-resolution TEM images of (a) SWNT-p and (b) SWNT-4. Ruler applies to both images

Figure 11 shows the electrochemical process of grafting aryl diazonium salts onto the carbon surface.

Figure 12 shows the sequence of derivatization reactions of single-walled carbon nanotubes with in situ generated diazo compounds and examples of functionalized phenyl moieties used for the reactions.

Figure 13 shows the absorption spectrum in dimethylformamide, (a) for SWNT-p and (b) for material 18. The spectra of materials 16, 17 and 19 are similar, with little or no visible peak structure. The spectra measured from materials in the order of making material 20 were substantially comparable to those shown for SWNT-p.

Figure 14 shows the Raman spectrum excited at 782nm for a solid sample. (a) for SWNT-p and (b) for material 17. The Raman spectra of materials 16, 18 and 19 are similar, differing only in the ratio of peak intensities. In all of the above cases, the relative intensity of the disordered modes increased, and the spectra measured from materials in the order of the prepared material 20 were substantially comparable to those shown for SWNT-p.

Figure 15 shows the sequence of photochemical derivatization reactions of single-walled carbon nanotubes.

Figure 16 shows an example that includes epoxy parts.

Figure 17 shows examples of nanotubes that are chemically modified with groups that are partially compatible with the curing agent and reactive with the epoxy portion of the thermoset resin.

Figure 18 shows a schematic diagram of a composite containing carbon nanotubes, where the freehand lines represent a polymer matrix crosslinked with chemically modified carbon nanotubes, resulting in a thermoset composite.

Figure 19 shows chemically modified carbon nanotubes cross-linked by disulfide bonds.

Figure 20 shows the preparation of nanotubes partially chemically modified with thiophenols.

Figure 21 shows the preparation of carbon nanotubes chemically modified with pendant epoxy groups. As shown in Figure 16, the groups are compatible with the epoxy portion of the resin and reactive with the curing agent portion of the thermoset resin.

Figure 22 shows an example of a composite material based on polymethyl methacrylate and chemically modified carbon nanotubes and based on hydrogen bonding (indicated by dotted lines in the figure).

Figure 23 shows an example of chemically modified nanotubes used in a polymerization process to grow polymers from nanotubes.

Description of Illustrative Embodiments

Derivatization Reaction of Carbon Nanotubes and Diazo Compounds

It is known that aryl diazonium salts can react with electron-deficient alkenes, which is called Meerwein reaction (Obushak, M.D. et al. Tett. Lett. 1998.39, 9567-9570). In such solution phase reactions, the decomposition of diazonium salts is generally catalyzed by metal salts such as cuprous chloride to give active aryl radicals. In some cases, the reaction is believed to proceed through the cation of the aryl group. This type of chemical process has been successfully used for the modification of carbon surfaces through the grafting reaction of electrochemically reduced aryl diazonium salts (Delamar, M. etc. Carbon 1997,35,801-807; Allongue, P. et al., J .Am.chem.Soc.1997, 119, 201-207; Ortiz, B. et al., J. Electro.Chem.1998, 455, 75-81; Saby, C. et al., Langmuir 1997, 13, 6805-6813; Delamar, M. et al., J. Am. Chem. Soc. 1992, 114, 5883-5884). The reduction reaction gives aryl radicals capable of forming covalent bonds with carbon atoms on the surface. This technique has been used for highly ordered pyrolytic graphite (HOPG) and glassy carbon (GC) electrodes.

Dichloromethane and acetonitrile were purified by distillation with calcium hydride. DMF was distilled and stored with molecular sieves. THF was purified by sodium/benzophenone ketyl distillation. All other chemical reagents were purchased from the market without further purification before use.

carbon nanotubes

Smalley et al., Nikolaev, P. et al. have developed methods for the preparation of small diameter (about 0.7 nm) single-walled carbon nanotubes (Chem. Phys. Lett 1999, 313, 91-97). This approach is disclosed in Smalley et al., U.S. Patent Application Serial No. 09/830,642, "Gas-Phase Nucleation and Growth of Single-Walled Carbon Nanotubes from High Pressure CO," filed April 27, 2001, which is commonly assigned To the assignee of this application, which is hereby incorporated by reference. This material is now commercially available (Carbon Nanotechnology, HiPco Materials). Since the diameter of these nanotubes is about the same as that of _C60 , it is understandable that these nanotubes are more active than the larger diameter nanotubes usually produced by the laser furnace method, because the activity of _C60 depends partly on the curvature strain. Although the invention also relates to multiwalled carbon nanotubes and larger diameter single walled carbon nanotubes, these small diameter nanotubes are primarily employed in the examples illustrating the method of the invention. Numerous diazonium salts have been employed, including those that provide moieties that facilitate further elaboration after nanotube attachment. Also oligophenylene (ethynylene) molecular elements similar to those exhibiting memory and having room temperature negative resistance (Chen, J. et al., App. Phys. Lett 2000, 77, 1224-1226) have been attached to nanotubes .

The following examples, as well as other examples described herein, further illustrate the invention and should not be construed as unduly limiting the scope of the invention.

A. Examples 1-11

For the electrochemical derivatization experiments, a piece of "Bucky paper" obtained by filtering the suspension was used as the working electrode of the three-electrode cell, immersed in the acetonitrile solution containing the diazonium salt and the electrolyte. The diazonium salts may be reduced to aryl radicals on the Baker paper surface, which subsequently form covalent bonds with the nanotubes. There is a lot of data on the conductivity of single-walled carbon nanotubes. In general, aryl diazonium salts are readily prepared under conditions that allow for a wide variety of functional groups. Thus, the method described here allows the functionalization of nanotubes with a wide variety of diazonium salts, including those that provide chemical treatments for re-elaboration after attachment to the nanotubes.

The purified single-walled nanotubes (herein referred to as SWNT-p) employed in this study contained little amorphous carbon or other exotic carbon impurities. Nanotube purification techniques are discussed in more detail below. The above facts are important. Because the presence of these substances would interfere with the ability to determine the success of the preceding derivatization. (Regarding the operability of the reactions, although the lack of impurities was a point of contention in earlier experiments, it must be pointed out that these reactions were performed with crude, unpurified multilayer and single-layer carbon nanotubes, i.e. carried out under the purification procedure.) Furthermore, the content of residual iron (catalyst from vapor phase growth technique) by electron probe microanalysis (EMPA) was <1 atomic % (about 0.3 atomic %). Figure 1 shows the diazonium salts used for SWNT-p derivatization. Compounds 1-7 and 11 were prepared from the corresponding aniline derivatives by known methods (Kosynkin, D; Tour, J.M.Org. Lett. 2000) using nitrosonium tetrafluoroborate as diazotizing agent. Compound 8 was prepared by the method reported by Kosynkin, D. et al. in Org. Lett. 2001, 3, 993-995. Compounds 9 and 10 were prepared according to the scheme shown in Figure 2. The characterization of these compounds is discussed further below. These compounds react with SWNT-p to form SWNT-x, where x is equal to 1-9 and 11-12, respectively.

The small-diameter single-walled carbon nanotubes used in this study are prepared with carbon monoxide as raw material and iron carbonyl as catalyst, using gas-phase catalytic technology (Nikolaev, P. et al., Chem.Phys.Lett.1999, 313, 91-97; U.S. Patent Application No. 09/830,642). (These carbon nanotubes are now commercially available; Carbon Nanotube Technologies, HiPco Materials). The production raw materials are purified by air oxidation at 150°C for 12 hours, and then annealed in argon at 800°C for 6 hours. This material was sonicated in concentrated hydrochloric acid (about 30 mg per 60 ml), filtered, washed well with water and 2-propanol, and dried under vacuum. The purity of these samples was identified by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electron microprobe analysis.

Baker Paper The use of Baker paper as a derivatized working electrode presents several unique problems. The electrical contact between the power source and the Baker paper is a problem during the electrochemical process. This situation was improved by applying colloidal silver paste to the spring clips holding the Baker paper. It is also believed that the success of the reaction depends at least in part on the quality of the Baker paper used as the working electrode. Therefore, it is beneficial to make Baker's paper suspensions with few or no visible particles prior to filtration.

General procedure for the diazotization reaction of aniline derivatives Weigh a portion of nitrosonium tetrafluoroborate (1.2 molar equivalents) in the glove box and seal it. After removal from the glove box, acetonitrile (3 ml/mmol aniline) was added and the solution was cooled to -30°C. A solution of the aniline derivative (1 molar equivalent) in acetonitrile (ca. 1 ml/mmol) was added dropwise with stirring (see below). In some cases, dry dichloromethane was used as a co-solvent for aniline derivatives. After the addition was complete, stirring was continued for 30 minutes, during which time the cooling bath was removed. After stirring for a total of 1 hour, the solution was diluted with two volumes of ether and stirred. The precipitate was collected by filtration and washed with ether.

4-Bromobenzenediazonium tetrafluoroborate (1). Yield: 85%, melting point 138°C. ¹ H NMR (400 MHz, CD ₃ CN) δ8.22 (ABq, J=9.1 Hz, Δv=102.1 Hz, 4H).

4-Chlorobenzenediazonium tetrafluoroborate (2). Yield: 78%, melting point 134°C. ¹ H NMR (400MHz, CD ₃ CN) δ8.24 (ABq, J=9.2Hz, Δv=214.2Hz, 4H).

4-Fluorobenzenediazonium tetrafluoroborate (3). Yield: 79%, melting point 160°C. ¹ H NMR (400 MHz, CD ₃ CN) δ 8.64 (dd, J = 9.4 Hz, 9.5 Hz, 2H), 7.69 (dd, J = 9.4 Hz, 9.5 Hz, 2H).

4-tert-butylbenzenediazonium tetrafluoroborate (4). 4-tert-Butylaniline was dissolved in a 1:1 mixture of acetonitrile and dry dichloromethane before addition to the nitrosonium tetrafluoroborate. Yield: 78%, melting point 91°C. IR (KBr) 3364.8, 3107.3, 2968.6, 2277.2, 1579.2, 1482.0, 1418.0, 1373.5, 1269.8, 1056.9, 841.1, 544.6, ^{621.4 cm -1} . ¹ H NMR (400MHz, CD ₃ CN) δ8.16 (ABq, J=9.0Hz, Δv=298.7Hz, 4H), 1.30(s, 12H). ¹³ C NMR (100 MHz, CD ₃ CN) δ 168.85, 133.67, 130.43, 111.88, 37.86, 30.84.

4-Nitrobenzenediazonium tetrafluoroborate (5). Yield: 67%, melting point 142°C. ¹ H NMR (400MHz, CD ₃ CN) δ8.72 (ABq, J=9.4Hz, Δv=65.4Hz, 4H).

4-Methoxycarbonylbenzenediazonium tetrafluoroborate (6) Yield: 80%, melting point 113°C. IR (KBr) 3103.8, 3042.4, 2955.3, 2294.7, 2310.1, 1731.4, 1582.9, 1439.5, 1306.4, 1045.23, 953.1, 860.9, 758.5, 666.3 ^{, 528.0 cm-1} . ¹ H NMR (400MHz, CD ₃ CN) δ8.51 (ABq, J=9.1Hz, Δv=77.9Hz, 4H), 3.97(s, 3H). ¹³ C NMR (100 MHz, CD ₃ CN) 165.02, 142.44, 134.12, 133.16, 119.77, 54.43.

4-tetradecylbenzenediazonium tetrafluoroborate (7). 4-Tetradecylaniline was dissolved in a 1:1 mixture of acetonitrile and dry dichloromethane before addition to the nitrosonium tetrafluoroborate. Yield: 69%, melting point 82°C. IR (KBr) 3103.8, 2919.5, 2289.6, 1577.8, 1473.7, 1070.8, 1024.8, 844.5, 813.8, 716.9, 541.0, 510.2 ^{cm -1} . IR (KBr) 3103.8, 2919.5, 2289.6. 1577.8, 1473.7, 1070.8, 1024.8, 844.5, 813.8, 716.9, 541.0, 510.2 ^{cm -1} . ¹ HNMR (400MHz, CDCl ₃ ) δ8.02 (ABq, J=8.8Hz, Δv=370.6Hz, 4H), 2.76(t, J=7.7Hz, 2H), 1.61(quin, J=7.8Hz, 2H) , 1.23(s, 22H), 0.85(t, J=7.0Hz, 3H). ¹³ C NMR (100 MHz, CDCl ₃ ) δ 159.92, 133.26, 131.94, 110.96, 37.49, 32.34, 30.87, 30.12, 30.10, 30.07, 30.04, 29.91, 29.78, 29.75, 29.72, 23.11, 14.55.

2-[2-(2-Methoxyethoxy)ethoxy]ethyl p-toluenesulfonate (13). Sodium hydroxide (3.65g, 91.3mmol) and 3(ethylene glycol) monomethyl ether (10.0g, 60.9mmol) were dissolved in a mixture of tetrahydrofuran and water (140ml, 20ml, respectively). The solution was cooled in an ice bath. A solution of a mixture of toluenesulfonyl chloride (12.76 g, 67. mmol) in 20 ml of tetrahydrofuran was added slowly. The solution was stirred at 0°C for 3 hours and then poured into 50 ml of ice water. It was extracted several times with dichloromethane. The combined organic layers were washed with dilute HCl and brine, and dried over magnesium sulfate. After filtration, the solvent was distilled off under reduced pressure to obtain 16.6 g of the product (86% yield). ¹ H NMR (400MHz, CDCl ₃ ) δ7.50 (ABq, J=7.9Hz, Δv=179Hz, 4H), 4.09 (appt, J=4.8Hz, 2H), 3.61 (appt, J=4.9Hz, 2H) , 3.55-3.52 (m, 6H), 3.47-3.46 (m, 2H). 3.30(s, 3H), 2.38(s, 3H). ¹³ C NMR (100 MHz, CDCl ₃ ) δ 145.21, 133.28, 130.21, 128.28, 72.20, 71.00, 70.85, 69.69, 68.95, 68.26, 59.31, 21.96. IR (pure) 3503.3, 2878.5, 1597.9, 1453.1, 1356.3, 1292.0, 1247.0, 1177.2, 1097.51019.0, 924.17, 818.0, 776.9, 664.5 ^{cm -1} .

4-{2-[2-(2-Methoxyethoxy)ethoxy]ethyl)nitrobenzene (14). A portion of compound 13 (9.0 g, 28.3 mmol) was dissolved in 50 mL of dimethylformamide. Potassium carbonate (11.75 g, 85.0 mmol) and 4-nitrophenol (3.82 g, 27.5 mmol) were added. The solution was stirred at 80° C. for 16 hours. After cooling to room temperature, the solution was poured into water, and then extracted three times with dichloromethane. The combined organic layer was first washed with water and then brine, and dried over magnesium sulfate. Filter again. The solvent was distilled off under reduced pressure. The product (5.71 g, 73% yield) was isolated by chromatography (silica gel, hexane:ethyl acetate, 1;2). IR (pure) 3109.2, 3078.2, 2878.5, 1726.3, 1588.1, 1511.2, 1337.1, 1106.7, 1050.3, 932.6, 845.5, 753.3, ^{656.1 cm -1} . ¹ H NMR (CDCl ₃ ) δ8.07 (d, J=9.3Hz, 2H), 6.88 (d, J=9.3Hz, 2H), 4.12 (app t, 2H), 3.79 (app t, 2H), 3.62 (m, 2H), 3.58-3.53 (m, 4H), 3.44-3.42 (m, 2H), 3.26 (s, 3H); ¹³ C NMR (100MHz, CDCl ₃ ) δ164.29, 141.93, 126.24, 114.99, 72.29, 71.29, 71.03, 70.98, 69.77, 68.60, 59.44.

4-{2-[2-(2-Methoxyethoxy)ethoxy]ethyl)aniline (15). One portion of compound 14 (5.77g, 20.2mmol) was dissolved in 40ml of acidic ethanol, and 10% palladium-carbon catalyst was added. The mixture was hydrogenated in a Parr apparatus (60 psi, 70° C.) for 3 hours. Then filter through diatomaceous earth (Celite), wash with ethanol, add solid sodium bicarbonate, stir for 2 hours and then filter. The solvent was distilled off under reduced pressure. A brown oil (5.0 g, 98% yield) was obtained. IR (pure) 3441.82, 3349.64, 2893.88, 2238.41, 1634.41, 1516.36, 1449.79, 1234.71, 1101.56, 906.97, ^{722.62 cm -1} . ¹ HNMR (400MHz, CDCl ₃ ) δ6.65 (ABq, J=8.7Hz, Δv=51.5Hz, 4H), 4.01(t, J=5.4Hz, 2H), 3.77(t, J=4.6Hz, 2H) ^C NMR (100 MHz, CDCl ₃ ) δ 152.30, 140.58, 116.75, 116.24, 72.31, 71.14, 71.02, 70.93, 70.30, 68.49, 59.44.

4-{2-[2-(2-methoxyethoxy)ethoxy]ethyl)benzenediazonium tetrafluoroborate (9). Compound 15 was diazotized as described above. The product was not in crystalline form, but a dark red, viscous material that was difficult to handle. The residue was mixed three times with ether, and the upper solvent was decanted slowly. As determined by ¹ H NMR, the material was quite pure and was used without further purification or characterization (2.17 g, yield 52%). ¹ H NMR (400MHz, acetone-d ₆ ) δ8.12(ABq, J=9.5Hz, Δv=479.5Hz, 4H), 4.53(app t, J=4.5Hz, 2H), 3.92(t, J=4.4 Hz, 2H), 3.68-3.66 (m, 2H), 3.61-3.56 (m, 4H), 3.46 (t, J=5.4Hz, 2H), 3.27 (s, 3H).

Compound 10. Add Boc ₂ O (17.6g, 80.6mmol), 4-aminothiophenol (10.0g, 80.6mmol), triethylamine (13.5ml, 96.7mmol), 150ml dichloromethane into a screw cap tube equipped with a magnetic stir bar Methane and N,N-dimethylaminopyridine (4.92 g, 40.3 mmol). The tube was purged with nitrogen, fitted with a screw cap, and the solution was stirred at room temperature for 24 hours. The solution was washed with 75 mL of water three times, and the organic layer was dried over magnesium sulfate, filtered and concentrated. The residue was chromatographed on silica gel using hexane:ethyl acetate (1.5:1) as eluent. After separation, the product was a transparent oil, which crystallized upon standing (16.16 g, yield 94%), with a melting point of 83-86°C. IR (KBr) 3454.5, 3376.8, 2978.6, 1711.4, 1630.1, 1597.4, 1500.0, 1384.4, 1296.0, 1201.0, 1176.3, 1125.4, 857.2, 825.2, ^{669.8 cm-1} . ¹ H NMR (200MHz, CDCl ₃ ) δ7.32 (d, J=8.6Hz, 2H), 6.70 (d, J=8.6Hz, 2H), 3.83 (brs, 1H), 4.54 (s, 9H). ¹³ CNMR (50 MHz, CDCl ₃ ) 169.72, 148.26, 137.05, 116.33, 115.89, 85.49, 28.63.

Compound 11. Into a 500ml round bottom flask cooled to -20°C was added 6.74ml BF ₃ OEt ₂ (171.9mmol). Then, a solution of compound 10 (3.0 g, 225.3 mmol) dissolved in 30 ml tetrahydrofuran (THF) was added over 10 minutes, followed by a solution of tert-butyl nitrite (5.59 ml, 103.12 mmol) in 20 ml THF. The solution was stirred, then heated to 0° C. for 40 minutes, during which time 400 ml of cold diethyl ether was added, and the precipitate was the desired product, which was collected by filtration and weighed 4.14 g (yield 96%). ¹ H NMR (400 MHz, CD ₃ CN) δ 8.52 (d, J=9.1 Hz, 2H), 8.0 (d, J=9.1 Hz, 2H), 1.54 (s, 9H).

4-Hydroxycarbonylphenyldiazonium tetrafluoroborate (12). This compound was prepared according to the general procedure (see above), sulfolane was used as a co-solvent for 4-aminobenzoic acid. Yield: 60%. IR (KBr) 3247.9, 3105.3, 2305.5, 1732.6, 1416.1, 1386.5, 1300.1, 1232.8, 1093.1, 996.1, 906.9, 872.0, cm ^-1 . ¹ H NMR (400 MHz, CD ₃ CN) δ 8.64 (d, J=9.0 Hz, 2H), 8.44 (d, J=9.0 Hz, 2H).

General steps of electrochemical derivatization of SWNT-p

The device used for the electrochemical derivatization reaction experiment is a three-electrode cell, with Ag/ _AgNO3 as the reference electrode and platinum wire as the counter electrode. A piece of Baker's paper (1-2mg) was used as the working electrode. Baker paper was prepared by filtering the 1,2-chlorobenzene suspension on a 0.2 μm polytetrafluoroethylene (PTFE) membrane (47 mm, Sartorius). After vacuum drying, the PTFE membrane was torn off, and one piece was cut for derivatization reaction. Baker paper was held by spring clips, which were previously treated with colloidal silver paste (Ted Pella Co.), and immersed in diazonium salts (0.5 mM for SWNT-1 to SWNT-7 and SWNT-9; for SWNT- 8 is 0.01M) and 4-n-butylammonium tetrafluoroborate (0.05M) in acetonitrile solution. Be careful not to immerse the spring clip itself in the solution. Apply an electrode potential of -1.0V for 30 minutes, avoid light, and pass nitrogen gas into the solution during the experiment. After the reaction, the part of the Baker paper that was not immersed in the solution was cut off, and the remaining part was soaked in acetonitrile for 24 hours. Then, it was washed with acetonitrile, chloroform and ethanol. After drying, the material was sonicated in acetonitrile solution for 20 minutes, filtered and washed with acetonitrile, 2-propanol and chloroform. The reaction products were vacuum dried at room temperature before characterization. Control experiments without diazonium salts confirmed that this reaction condition did not affect the nanotubes, as identified by ultraviolet/visible/near-infrared spectroscopy (UV/VIS/NIR), Raman spectroscopy, and thermogravimetric analysis.

Other salts and parameters

In the method of the present invention, a large number of various aryl diazonium salts are used for chemical modification. In addition, parameters such as the applied electrode potential, the length of time the potential is applied, the solvent, the supporting dielectric, etc. can be varied. Furthermore, alkyl, alkenyl and alkynyl diazonium salts may also be added in the process of the present invention.

B. Characterization

Scanning electron microscopy (SEM) experiments were performed on an ESEM XL-30 from Phillips at an accelerating voltage of 50,000V. The instrument is equipped with an EDAX detector. The sample for transmission electron microscopy imaging was dropped from tetrahydrofuran onto a 200-mesh lacey carbon grid on a copper support and dried. The accelerating voltage was 100kV. On the solid sample, excited at 782nm, the Raman spectrum was performed with a Raman spectrometer from Renisaw Company. The UV/VIS/NIR absorption spectrum was collected with a dual-beam UVPC-3101 instrument from SIMADZU, and the solvent was used as a reference. Fourier transform infrared spectra (FT-IR) were collected with an attenuated total reflectance (ATR) attachment. Thermogravimetric analysis (TGA) data were collected on a SDT-2960 from TA Corporation with argon gas. AFM experiments were performed on a digital multimode scanning probe microscope using tappimg mode. These experimental samples were dispersed by ultrasonic vibration and spin-coated on freshly cleaved mica substrates. Electron probe microanalysis (EMPA) was performed using Cameca SX-50. The instrument was calibrated, and the data were collected from several different points on each sample, and then averaged and presented. NMR data were collected with a Bruker Avance 400. Chemical shifts are expressed in ppm downfield from tetramethylsilane (TMS) and referenced to solvent. Melting points are uncorrected.

Electronic structure and optical properties

The electronic structure and optical properties of single-layer carbon nanotubes have been fully studied (Liang, W.Z. et al., J.Am.Chem.Soc.2000, 122, 11129-11137; Jost, O., etc., Appl.Phys.Lett. 1999, 75, 2217-2219; Wu. J. et al., Appl. Phys. Lett. 2000, 77, 2554-2556). Figure 3 shows the UV/Vis/NIR absorption spectra of SWNT-p and SWNT-1. The characteristic peak part (Van Hove band) in the spectrum of SWNT-p arises from the density of states (DOS) singularity, and the characteristic peaks in this spectral region are attributed to the energy level transition of semiconductor nanotubes. The width of these peaks is due to the overlap of lines generated by nanotubes of different diameters and the chiral index. The bandgap transition of SWNT-1 is no longer seen, and its spectrum is essentially featureless. The absorption spectra of SWNT-2 to SWNT-7 are very similar to those of SWNT-11 to SWNT-12, without obvious characteristic peaks. There are still visible characteristic peaks in the spectra of SWNT-8 (Fig. 4) and SWNT-9, but they are obviously weakened compared with SWNT-p. The loss of peak structure in this absorption spectrum indicates that the nanotube has obvious electronic perturbation, and the extended π network structure is broken. This result is most consistent with the occurrence of covalent bonding of functional groups, rather than simple adsorption of nanotube sidewalls or end caps.

Raman spectroscopy

The Raman spectrum of single-layer carbon nanotubes has also been fully studied theoretically and experimentally (Richter, E., etc., Phys.Rev.Lett.1997, 79, 2738-2740; Rao, AM, etc., Science 1997, 275, 187-191; Li, HD et al., App. Phys. Lett. 2000, 76, 2053-2055). The Raman spectrum of SWNT-p (Fig. 5A) showed two strong bands. Radial ventilation mode (ω _r ~ 230cm ^-1 ) and tangential ventilation mode (ω _t ~ 1590cm ^-1 ). The multiple peaks seen in the radial ventilation mode may be caused by the diameter distribution of nanotubes in the sample. The weaker band at about 1290cm ^-1 (ω _d ) in the center is caused by the disordered arrangement of carbon atoms in the hexagonal framework of the nanotube wall or sp ³ hybridization. A weak band ^at 850 cm is also characteristic of these small-diameter nanotubes, although its molecular origin has not been determined. The spectrum of SWNT-1 (Fig. 5B) is quite different. In particular, the relative strength of the disordered modes is much greater, a consequence of the introduction of covalently bonded moieties into the nanotube framework, within which a considerable number of ^SP2 carbons have been converted to ^SP3 hybridization. The Raman spectra of other functionalized materials show similar modification effects with respect to SWNT-p, only in different degrees. Table 1 lists the frequencies of the disordered modes and their relative intensities of the three main bands.

Table 1 Frequency and main peak intensity ratios of disordered modes in Raman scattering experiments compound ω _d Intensity ratio (ω _γ : ω _d : ω _t ) ^{a, b} SWNT-p 1291 1.0:0.3:2.7 SWNT-1 1295 1.0:2.2:3.3 SWNT-2 1294 1.0:2.2:4.0 SWNT-3 1295 1.0:2.0:4.0 SWNT-4 1290 1.0:1.4:3.7 SWNT-5 1291 1.0:1.4:3.7 SWNT-6 1292 1.0:1.5:3.5 SWNT-7 1293 1.0:1.3:3.8 SWNT-8 1292 1.0:0.7:3.0 SWNT-9 1293 1.0:0.8:2.5 SWNT-11 1292 1.0:0.8:2.9 SWNT-12 1291 1.0:1.0:3.4

a.ω _γ = radial ventilation pattern ω _d = disordered pattern ω _t = tangential pattern

b. ωγ intensity is measured at 265cm ^-1 , and other intensities are measured at the maximum value.

The frequency of the disordered mode did not change significantly, while the intensity of the peaks in this mode increased in all cases relative to those of the other two modes. The intensity of the tangential mode relative to the radial ventilation mode was also increased in all cases. In some cases, Raman spectra collected after functionalization revealed changes in the relative intensities of peaks in the radial ventilation mode region. For example, Figure 6 shows the Raman spectra of SWNT-p and SWNT-4 in this region.

IR

Infrared spectroscopy (Fourier transform infrared spectroscopy, attenuated total reflectance (FT-IR, ATR)) was also used to characterize some derivative compounds. The IR spectrum of SWNT-4 (Fig. 7A) clearly shows a stretching of the CH bond from the tert-butyl moiety at about 2950 cm ⁻¹ . In the spectrum of SWNT-6 (Fig. 7B), it can be seen that there is carbonyl stretching at 1731cm ^-1 (the precursor of diazonium salt is at 1723cm ^-1 ), and there is a weak CH stretching at 2900cm ^-1 .

Electron Probe Microanalysis

Electron probe microanalysis (EMPA) experiments revealed that SWNT-2 (average of four probe points) contained 2.7 atomic % chlorine and SWNT-3 (average of five probe points) contained 3.5 atomic % of fluorine. These two percentages correspond to estimated stoichiometric values of CR _0.036 in SWNT-2 and CR _0.05 in SWNT-3, respectively, where C represents the carbon in the nanotube framework and R is the functionalization moiety. Thus, there is approximately one functional group moiety for every 20-30 carbon atoms in the nanotube.

Thermogravimetry

In thermogravimetric analysis (TGA) of SWNT-2 (Fig. 8), under argon, heated to 600°C, a total weight loss of about 25% was observed. As shown in Figure 9, after the thermogravimetric analysis of SWNT-2, its Raman spectrum returned to a situation similar to that of SWNT-p. This recovery can be considered to indicate that the functional groups have been partially removed, leaving only the nanotubes themselves. Sample stoichiometry estimated by electron probe microanalysis indicated that removal of this functional moiety resulted in a weight loss of about 25%. Therefore, the data fit very well. The thermogravimetric analysis results of SWNT-3 are also in good agreement with the electron probe analysis results. SWNT-p loses about 5% weight under the same temperature distribution. Table 2 shows the TGA data and estimated stoichiometry of the remaining compounds (except SWNT-8 as it was not tested).

Table 2 Frequency-to-intensity ratios of disordered modes Measurements% stoichiometric value compound weightlessness Ratio ^a SWNT-p 5 none SWNT-1 35 1/25 SWNT-2 30 1/27 SWNT-3 26 1/20 SWNT-4 27 1/34 SWNT-5 26 1/31 SWNT-6 31 1/28 SWNT-7 39 1/36 SWNT-8 -- -- SWNT-9 36 1/40 SWNT-11 28 1/44 SWNT-12 twenty four 1/32

a Nanotube carbon with functionalized phenyl moieties. These data have been corrected for weight loss due to solvent evaporation and degassing at low temperatures (approximately 2-4% in all cases).

Table 2 reflects the functionality of these compounds as being at least about one functional moiety per 40 carbon atoms, typically at least about one functional moiety per 30 carbon atoms. Nanotube functionality is estimated to carry approximately one functional group moiety for every 20-30 carbon atoms.

SEM and TEM

Due to the low resolution, scanning electron microscopy (SEM) analysis of the reaction products did not reveal any visible functionalization or significant changes in SWNT-p. Transmission electron microscopy (TEM) imaging of SWNT-4 revealed clear changes due to functionalization. In the image of SWNT-p (FIG. 10A), the nanotube walls are substantially clear and uniform, and there is no overcoat of graphitic carbon. The .SWNT-4 image (FIG. 10B) reveals protrusions on the sidewalls of the nanotubes, the size of which is +2-6 Å. These protrusions were visible on nearly all individual nanotubes as well as on the outside of the nanowires, although resolution was not sufficient to determine whether they were on the tube walls embedded within the wires. But these features are the result of functionalization.

Solubility

The solubility of single-walled carbon nanotubes is the part of most interest to those skilled in the art of the present invention. The three most commonly used solvents for underivatized small-diameter nanotubes are dimethylformamide, chloroform, and 1,2-dichlorobenzene. SWTN-4 was the only material that was found to have significantly improved solubility in organic solvents. This material is slightly soluble even in tetrahydrofuran (THF), whereas SWNT-p, on the contrary, is completely insoluble in this solvent. After ultrasonic oscillation for about 30 minutes, it can be found that the THF solution contains about 50 mg/L of SWNT-4, and there are no visible particles. After 36 hours, some visible particulate matter had appeared, but the solvent was still almost black, a color that lasted at least several weeks. In dimethylformamide, the solubility of chloroform and 1,2 dichlorobenzene is also improved, and the suspension is formed faster than SWNT-p, thereby obtaining a higher concentration. It is thought that the improvement in solubility may be hindered by the bulky tert-butyl group, which inhibits the intimate contact necessary for "wire formation" of the nanotubes.

SWNT-5 and SWNT-8 were more soluble in dimethylformamide, but the solubility in other solvents (tetrahydrofuran, toluene, 2-propanol, carbon disulfide) did not improve. SWNT-9 was prepared mainly to improve its solubility in water and other hydrogen-bonding solvents. However, the functionalization results in the opposite. SWNT-9 is not dispersed in water or water/0.2% Triton x. Considerable difficulty was encountered in making a suspension of SWTN-9 in dimethylformamide.

strength

SWNT-1 was subjected to various conditions in assessing functionalization strength and preventing simple entrainment or adsorption. The material was ultrasonically shaken in chloroform and 1,2-dichlorobenzene at room temperature and 45°C for 10 minutes, filtered, and spectroscopically identified, no detectable change was found. In addition, SWNT-1 was sonicated in 1,2-dichlorobenzene for 10 minutes to disperse the nanotubes, and then stirred at 75 °C for 3 hours. After filtration and washing, no spectral change was found.

In addition, SWNT-3 was ultrasonically oscillated in acetonitrile, filtered and washed, and then subjected to electron probe microanalysis. The fluorine content was 3.6 atomic %, compared with the previous 3.5 atomic % (see above), it was still within the experimental measurement error range .

C. Mechanism of Derivatization

Without intending to be bound by theory, it is believed that the functionalization described here is likely to be initiated in a manner similar to that shown in FIG. 11 . It is hypothesized that the reduction generated aryl radicals react with the nanotubes so that neighboring radicals can react further or be quenched by solvent or some impurities or hydrogen. The tendency of the initial aryl radical to dimerize or abstract a hydrogen atom from the solvent is minimized by generating the aryl radical at the surface of the nanotube for the desired reaction. It should be pointed out that although the reaction can be carried out by aryl cations, the reaction mechanism is independent of the final product.

Here the main advantage of using the electrochemical method is that, in contrast to the solution phase method, it does not require copper or other metals to catalyze the reduction of diazonium salts. Due to the low concentration of nanotubes in the solution, it is possible that the aryl radicals are quenched by some other components. In this case, dimerization of nanotubes is unlikely to occur due to the lack of mobility of nanotubes in solid materials.

Thermal Derivatization Reaction of Carbon Nanotubes and Diazonium Salts

Derivatization reactions with aryl diazonium salts are not limited to electrochemically induced reactions, i.e. direct treatment of monolayer carbon nanotubes with tetrafluoroborate aryl diazonium salts in solution, and in situ generation of diazonium salts with alkyl nitrites It is an effective means of functionalization. The advantage of in situ generation of diazonium salts is that this method avoids the necessity of isolating and storing potentially poorly stable or photosensitive aryl diazonium salts. The thermal reaction process employs temperatures up to about 200°C, usually up to about 60°C. In some cases it has been observed that direct treatment with the preformed diazonium salt is effective at moderate temperatures or even at room temperature, and it is expected that the reaction temperature may be lower than room temperature.

A. Examples 12-17

The nanotubes used in this study are still prepared by the gas-phase catalytic method developed by Smalley et al. and are now commercially available (Carbon Nanotechnology, HiPco Materials). The method for the purification of production raw materials is to oxidize in humid air at 250°C for 24 hours, then stir in concentrated hydrochloric acid at room temperature for 24 hours, the formed material is first washed with a large amount of water, then with 10% aqueous sodium bicarbonate solution, Wash again with water. After vacuum drying, the material was ready for functionalization reactions.

Figure 12 shows the sequence of reactions. In a typical test, about 8 mg of single-walled carbon nanotubes were placed in 10 ml of 1,2-dichlorobenzene (ODCB) and ultrasonically oscillated for 10 minutes. Add the solution of aniline derivative (2.6mmol, about 4 g equivalent/mole carbon) in 5ml of acetonitrile to this suspension, transfer the feed solution to the reaction tube (Ace Glass Company, #8648-03) covered with septum and use After bubbling nitrogen for 10 minutes, 4.0 mmol of isoamyl nitrite was quickly added, the septum was removed and replaced with a Teflon screw cap, and the suspension was stirred at 60°C for about 15 hours. Because the reaction system will discharge nitrogen, the container will reach a considerable pressure, so in the first three hours of the reaction, the reaction tube cover should be slightly unscrewed about every 30 minutes to reduce the pressure in the container.

After cooling to about 45°C, dilute the suspension with 30ml of dimethylformamide (DMF), filter through a Teflon membrane (0.45μm), wash thoroughly with DMF, repeat ultrasonic oscillation, and then wash with DMF to ensure the purity of the material .

B. Characterization

The derivatized nanotube materials 16-19 and 21 were similar to those reported for the electrochemically derivatized materials described above, showing significant changes in spectral properties. For example, the UV/Vis/NIR absorption spectrum (Fig. 13) of material 18 shows almost complete loss of von Hove singularity. modified. In the Raman spectrum shown in Fig. 14, the total intensity of the scattered light is low, and the relative intensities of the three main modes are changed.

Relative to the tangential mode at about 1590 cm ^-1 , the intensity of the radial ventilation mode (about 250 cm ^-1 ) is reduced, and the intensity of the disordered mode (1290 cm ^-1 ) is clearly enhanced. The increase in the relative strength of the disordered pattern is due to the increase in the number of SP ³ hybridized carbon atoms in the nanotube framework and thus can be taken as a rough estimate of the degree of functionalization. Furthermore, as previously discussed, the functionalized phenyl moieties attached to the nanotubes can be removed by heating in an argon atmosphere, and thus thermogravimetric analysis (TGA) enables quantitative estimation of the degree of functionalization. Materials 16-19 were heated to 600°C in an argon atmosphere, and the following are the measured weight loss values. The values in parentheses are the values previously reported for the same material prepared by electrochemical methods: Material 16: 26% (30 %), material 17: 25% (27%), material 18: 26% (31%), material 19: 23% (26%), material 21: (not prepared by electrochemical method). Material 20 did not show a similar change in spectral properties, and thermogravimetric analysis indicated significant mass loss. Although this functional group has been successfully attached to nanotubes by electrochemical methods. The successful preparation of ester-bearing material 18 provided in principle the utilization of the carboxylic acid moiety by hydrolysis.

Comparing the degree of functionalization obtained by the thermally induced method with the degree of functionalization obtained by the electrochemical method is of primary interest in the present invention. Experiments Nos. 13-18 were carried out with a large excess of the aniline derivative, ie sufficient to provide the diazonium salt in an amount equal to that employed in the previously reported electrochemical examples. Thus, Examples 13-18 can be compared in this manner.

For material 16, a direct comparison was made using electron probe microanalysis. The analysis gave 2.2 atomic % of chlorine relative to 97 atomic % of carbon. A similar material prepared electrochemically was analyzed to contain 2.7 atomic % chlorine relative to 96 atomic % carbon (see above).

Thermogravimetric analysis data can provide additional insight into the relative efficiency of thermochemical induction methods. For example, the mass loss in material 19 corresponds to an estimated 1 in 37 carbon atoms in the nanotube being functionalized, compared to 1 in 34 for the electrochemical method. It can be considered that the efficiency of the thermal induction technique is not much different from that of the electrochemical method for the same material (SWNT-5). It is also believed that the optimization of conditions can increase the degree of functionalization. The measured efficacy is sufficient to significantly alter the properties of monolayer nanotubes, potentially satisfying many application requirements, such as the formation of cross-linked materials and composites discussed below.

It can be found that the thermal reaction of the present invention is almost as effective as the electrochemical method of the present invention, although in some respects the thermal reaction is simpler to operate and more suitable for scalability.

It should also be noted that chemical derivatization of nanotubes using preformed diazonium salts has also been successful. Diazonium salts can be pre-prepared and added to the mixture after separation. However, a heat-induced derivatization reaction is employed. Other variables include the temperature of the reaction process (room temperature, lower and higher temperature), ratio of reactants and type of organic solvent.

Photochemical Derivatization of Carbon Nanotubes and Diazonium Salts

Example 18

Derivatization reactions with aryldiazonium salts can also be induced photochemically. The photochemical reaction can also be carried out with the tetrafluoroborate 4-chlorobenzene diazonium salt adopted and prepared in Example 2. Therefore, a suspension of SWNT-p in 1,2-dichlorobenzene was generated by sonication. To this suspension was added a portion of the diazonium salt dissolved in a minimal amount of acetonitrile. The obtained mixed solution is placed in a photochemical reaction chamber for stirring. The excitation wavelength is 254nm (ultraviolet light source). The light source used for the photochemically induced reaction can be light of any wavelength, usually ultraviolet light or visible light. Figure 15 shows this reaction. The resulting material was similar in all respects to SWNT-2 prepared electrochemically according to the present invention.

This experiment further confirms that the reaction of diazonium salt leads to covalent attachment to nanotubes.

Controlled Positional Functionalization of Carbon Nanotubes with Diazonium Salts

By adopting the photochemical induction reaction of the present invention, the derivatization reaction of the nanotube can be controlled at a specific position. Prior Art (M.S.Fuhrer et al., "Crosslinking of Nanotubes" Science, 288, 21 April 2000, P494; Yu Huang et al., "Direct Assembly of One-Dimensional Nanostructures in Functional Networks" Science 291, 26January 2001, P630 ; Yi Cui et al., "Nanoscale electronic components assembled with silicon nanowire building blocks" Science, 291, 2 February 2001, P851) can be used to prepare nanotube cross structures, wherein one nanotube is fixed on the substrate, and Another nanotube is suspended not far above it. The two nanotubes are individually addressable electrically. Applying a substantially opposite potential between them causes the upper nanotube to deform and bring it substantially into contact with the lower nanotube. The term "contact" as used here refers both to the actual physical contact of the two, but also to the close proximity of entities over an infinitesimal distance (called van der Waals contact), where the entities influence each other at the molecular and electronic levels .

This deformation results in two meaning features. First, the physical deformation of the upper nanotube, based on the current understanding of the effect of curvature strain on activity, may lead to higher chemical activity at the deformation. This feature allows selective functionalization at the junctions via electrochemical reaction techniques with diazonium salts. Second, the potential is higher at the junction between the two tubes.

In the present invention, the intersection can be directly performed by applying a potential at both ends of the nanotube in the presence of α, ω-double nitrogen salt or a single diazonium salt with an interacting group at the other end that allows functionalization at the intersection microdomain. Functional reactions at nanotube junctions.

Any intersecting array of nanotubes can be functionalized by such methods. For example, nanotube intersections are fabricated by fluid flow over a patterned substrate or by direct tube growth between pillars or by other methods. Furthermore, the diazonium salt assembly described here may occur in diazonium salt solutions under the application of a voltage across the orthogonal nanotubes, regardless of the way the nanotube arrays are assembled. Applying a voltage to the nanotubes in the presence of a diazonium salt allows functionalization at the junction domains.

The diazonium salt reacts with the nanotube surface through potential steering at the junction, thereby placing a functional molecular element at the junction. Positional functionalization could enable nanotubes to be used in molecular-scale electronic applications, since the functionality of elements at intersections is critical. Thus, intersecting nanotubes provide a means of directly addressing functionalized molecules, including molecules that function as molecular switches, molecular wires, and among other capabilities and uses generally known in the art.

Moreover, the method also allows different molecules to be attached to the junctions of the nanotubes, that is, two or more different chemical functional groups to be attached to different parts of the nanotubes in a controlled manner. This connection is accomplished by applying a potential at a given set of locations in the first diazonium salt solution, then moving to the second diazonium salt solution, applying potentials at other locations, etc. In addition, positional functionalization allows individual molecules or groups of molecules to be addressed electrically by metal contact thermal or other contact means known in the art. Just incorporating this electronically important molecule into SWNT-8 is.

Application of chemically modified carbon nanotubes in polymer/composite materials

Polymers and polymer/composites are widely used as structural materials and various other applications. Derivatized carbon nanotubes made by the methods disclosed in this invention can be used with existing polymer matrices to form new polymer/composite materials. In general, possible composites can be made from chemically modified nanotubes with thermoplastics, thermosets, elastomers, and other materials. The polymer matrix has a wide variety of chemical structures, namely polyethylene, various epoxy resins, polypropylene, polycarbonate, etc. There are also many possible variations in the chemical groups that can be attached to the nanotubes. Therefore, it is possible to select a specific polymer and specific moiety to enhance the properties of the desired specialty polymer/composite.

Accordingly, the polymer/composite will have significantly enhanced properties, such as enhanced strength and/or electrical conductivity. Also, after modification by suitable chemical groups, the nanotubes are chemically compatible with the polymer matrix, enabling the properties of the nanotubes (especially mechanical strength) to be substantially transformed into properties of composite materials. Usually, for this purpose, the modified carbon nanotubes are thoroughly mixed (physically blended) with the polymer material and allowed to react at room temperature or higher.

Thermosets may require the formation of polymers/composites in which the carbon nanotubes are chemically bonded to the polymer (thermoset) at multiple points. For example, epoxy resin is used to realize. Epoxy resins usually consist of two parts mixed in a certain ratio. The mixture then hardens or "cures" over a period of time into an adhesive or structural material. These two parts are the epoxy part (labeled A in Figure 16, which is obtained in this example from the reaction of bisphenol-A (bisphenol-A) with epichlorohydrin) and the curing agent (labeled B in Figure 16). The curing agent contains chemical groups that react with recurring chemical groups in the epoxy moiety, ie the cured or crosslinked resin is formed from A (especially terminal epoxide functional groups) and B (especially terminal amine functional groups). Thus, both the epoxy moiety and the curing agent contain many reactive groups, forming a "cross-linked" material with many chemical bonds, giving the cured material (labeled C in Figure 16) its strength. The reaction product is a highly crosslinked thermoset.

There are a wide variety of epoxy components on the market, and the chemical structures of the A and B parts vary greatly. For example, curing agents may be based on diamines, polythiols, phenolic-containing substances, etc., and may be polymeric. The addition of chemically modified carbon nanotubes to such systems greatly enhances the strength of the resulting material due to the strength of the nanotubes themselves. The nanotubes can be chemically modified with either genetically compatible groups that are partially compatible with epoxy or with groups that are partially compatible with curing agents. For example, Figure 17 shows the modified nanotubes after fabrication. (The shaded bars in the figure represent carbon nanotubes).

The carbon nanotubes modified in this way are fully mixed with the curing agent part or the epoxy part. The homogenized material is then thoroughly mixed with the second part and allowed to react, or to cure at room temperature or at elevated temperatures, depending on the particular system. The resulting composite can then be crosslinked not only with the curing agent, but also with the modified carbon nanotubes bonded by aryl sulfide as shown in FIG. 18 . The freehand lines in the figure represent the polymer matrix.

Such materials can be prepared using various modified carbon nanotubes, and Figure 17 is a schematic illustration of an example. The linkage between the polymer matrix and the nanotubes can be an ether, thioether, amine, salt bridge (such as SWNT-11 in an amine-containing polymer host), or other linkages. It is understood that the direct chemical bonding of the nanotubes to the surrounding polymer matrix allows the transfer of the strength properties of the nanotubes to the composite material. It should also be pointed out that the enhancement of material properties induced by nanotubes may also be caused by factors other than this direct chemical bonding; for example, functionalization can also improve the dispersion of nanotubes in the polymer matrix.

In addition to the chemical bonds between the nanotubes and the surrounding polymer matrix, in the case of thiophenol-derivatized nanotubes, there is also the interaction chemistry of the nanotubes themselves. As shown in Figure 19, disulfide bonds formed between the nanotubes further act as strengthening materials. The disulfide bonds can be further reduced (eg, chemically) to form non-crosslinked nanotubes again. Therefore, this is a stealty like crosslinking. In fact, such crosslinked nanotubes show themselves to be reinforcing materials for some applications.

Another possibility, as shown in Figure 21, is to modify the carbon nanotubes with chemical groups that are partially compatible with the epoxy but not with the curing agent. The material formed by adding nanotubes derivatized in this way is also a chemically bonded, three-dimensional network structure cross-linked with curing agents and chemically modified nanotubes.

Other specific interaction chemistries between modified carbon nanotubes and polymer matrix are also possible, for example, a system based on hydrogen bond interactions is shown in Figure 22. Such interactions impart nanotube strength to the composite in an extended three-dimensional network.

Using the electrochemical method described in the present invention, the derivatized nanotubes shown in Figure 20 were prepared. It can thus be considered that treatment with trifluoroacetic acid in 1,2-dichlorobenzene (acidolysis) completes the deprotection of the thiol. Alternatively, this step can be accomplished by treatment with trifluoroacetic acid in dimethylformamide, or by pyrolysis at or about 175°C. Also, as shown in Figure 20, the formed functionalized nanotubes can be chemically reacted with, for example, epoxy resins with free thiol (SH) groups acting as crosslinkers.

Thermoplastics In addition to thermosets, derivatized nanotubes can also be used in thermoplastics. As in the case of thermosets, the derivatized nanotubes may or may not form chemical bonds with the polymer matrix. It will be appreciated that moderate chemical linkage between the derivatized nanotubes and the polymer matrix is permissible as long as the properties of the thermoplastic are preserved (particularly heat resistance and improved material performance without significant degradation). As noted above, the physical blending of carbon nanotubes with polymers is enhanced by derivatization methods (specifically by making the nanotubes more compatible with, or more soluble in, the polymer host).

For example, polymers/composites are required to contain pure (underivatized) single-walled carbon nanotubes to impart some enhanced conductivity to the polymer; however, pure underivatized carbon nanotubes are not sufficiently dispersed in the polymer. The nanotubes are derivatized with special moieties, after which the nanotubes are fully dispersed. Since the derivatization reaction of the nanotubes may affect the conductivity of the nanotubes (and thus the conductivity of the polymer/composite material), it is best to reverse the derivatization reaction after the nanotubes are dispersed to remove the functional groups on the nanotubes . The electrical conductivity of the material can be restored in this way. Any method of reversible derivatization can do this, such as raising the temperature of the polymer/composite to a temperature that dissociates the functional groups. Typically this temperature appears to be at least about 250°C.

A. Examples 19-25

Furthermore, thermoplastics can also be formed using derivatized carbon nanotubes. While the functional groups are not necessarily chemically bonded to the polymer, the functional groups can be physical extensions of the nanotubes (like dendrites) providing additional strength to the polymer/composite. This enhancement is due to the roughening effect of the nanotube surface, which increases friction and reduces the sliding of the polymer matrix along the length of the nanotube. This effect further transfers desired nanotube properties to the composite, as is known in the art.

The following functionalized single-walled carbon nanotubes were prepared using the method discussed above, where n is one functional group per 20-40 nanotube carbon atoms.

This derivative material (17) is dispersed in high impact polystyrene (HIPS) in various concentrations. Tensile strength, tensile modulus, and percent strain at break data were collected for the composite material formed. Table 3 is the results of these examples.

table 3 Material Tensile strength (MPa) Tensile modulus (MPa) % strain at break HIPS (pure) 18.1 454.4 56.4 1% by weight material 17 32.5 729.3 4.6 3% by weight material 17 17.8 821.3 2.2 3% by weight pristine ^* 22.8 560.0 11.0 5% by weight material 17 26.3 736.5 3.9 7% by weight material 17 22.0 724.4 3.1

*3% by weight, unfunctionalized nanotubes (SWNT-p), for comparison.

The tensile properties of polymers/composites with functionalized nanotubes are generally significantly improved. Improvements were made for pristine and HIPS polymers, and for composites of HPIS and unfunctionalized nanotubes.

Polymerization Furthermore, polymers containing carbon nanotubes can be formed by derivatizing functional groups capable of polymerizing or initiating polymerization with carbon nanotubes. Once the functional groups are attached, the polymer can be grown in situ from the functional groups using standard polymerization techniques, ie the functional groups attached to the nanotubes can be used as generators for polymer growth. The so-called standard polymerization technique can be any one of the known standard techniques such as free radical, cationic, anionic, polycondensation, ring opening, metathesis or ring opening metathesis (ROMP) polymerization, if suitable functional groups are bonded to the nanotubes superior. For example, Figure 23 is an example of carbon nanotube hexa+ derivatization reaction with 4-aminophenyl functional group, followed by polymerization with styrene to grow polymers from functional groups. Thus, the functional groups attached to the nanotubes become chemically active moieties for polymerization, thereby creating a composite chemically containing the nanotubes.

All components and methods disclosed and claimed herein are presented in light of the teachings herein and can be practiced without undue experimentation. The compositions and methods of the invention are described herein according to preferred embodiments. It will be apparent to those skilled in the art that changes may be made in the components, methods, and method steps and order of steps described herein without departing from the principles, spirit and scope of the invention. More specifically, certain chemically and physiologically related reagents may be substituted for those described herein so long as the same or similar results are obtained. All such similar substitutes and modifications apparent to those skilled in the art are deemed to be within the spirit, scope and principle of the invention as defined by the appended claims.

Claims (62)

1. A derivation method of carbon nanotube sidewall, said method comprising: (a) selecting carbon nanotubes; and (b) reacting the carbon nanotubes with a diazo compound to form derivatized carbon nanotubes, the reaction being selected from electrochemically induced reactions, thermally induced reactions and photochemically induced reactions. 2. The method of claim 1, wherein the carbon nanotubes are single-walled carbon nanotubes. 3. The method of claim 2, further comprising dispersing the derivatized carbon nanotubes in a solvent. 4. The method according to claim 2, characterized in that, the method further comprises generating the diazo compound in advance. 5. The method of claim 2, wherein the method comprises: (a) mixing a precursor of a diazo compound with the single-walled carbon nanotubes; (b) Formation of diazo compounds. 6. The method of claim 2, wherein the single-layer nanotubes react electrochemically with the diazo compound. 7. The method of claim 2, wherein the single-walled carbon nanotubes react thermally with the diazo compound. 8. The method of claim 2, wherein the single-walled carbon nanotubes react photochemically with the diazo compound. 9. The method of claim 2, wherein the diazo compound comprises an aryl diazo compound. 10. The method of claim 2, wherein the diazo compound comprises a compound selected from an alkyl diazo compound, an alkenyl diazo compound, an alkynyl diazo compound or a combination thereof. 11. The method of claim 1, wherein the carbon nanotube is a carbon nanotube assembly, and the method further comprises (a) immersing the carbon nanotube assembly in a solution containing a diazo compound; and (b) applying an electrical potential to the nanotube assembly. 12. The method of claim 11, wherein the potential is a negative potential. 13. The method of claim 11, wherein the solution further includes a substance to support the electrolyte. 14. The method of claim 2, wherein the diazonium compound comprises a diazonium salt. 15. The method of claim 14, wherein the diazonium salt comprises a compound selected from aryl diazonium salts, alkyl diazonium salts, alkenyl diazonium salts, alkynyl diazonium salts or combinations thereof Salt. 16. The method of claim 2, wherein the amount of moieties bonded to carbon atoms of the carbon nanotube is such that the ratio of said moieties to carbon atoms is at least about 1:40. 17. The method of claim 2, wherein the amount of moieties bonded to the carbon atoms of the carbon nanotube is such that the ratio of moieties to carbon atoms is at least about 1:30. 18. The method of claim 2, wherein the reaction is a thermal reaction at a temperature of up to about 200°C. 19. The method of claim 2, wherein the reaction is a thermal reaction at a temperature of up to about 60°C. 20. The method of claim 2, further comprising removing functional moieties from the derivatized nanotubes. 21. The method of claim 20, wherein the derivatized nanotubes are heated to at least about 250°C. 22. The method of claim 8, wherein the photochemical reaction comprises the use of an ultraviolet light source. 23. The method of claim 8, wherein the photochemical reaction comprises the use of a visible light source. 24. The method of claim 5, wherein the precursor of the diazo compound is a precursor of aniline derivatives of the diazo compound, and it reacts with nitrite to form the diazo compound. 25. The method of claim 2, wherein a molecule is covalently bonded to the derivatized carbon nanotube, wherein the molecule is operable in a capability selected from molecular switches, molecular wires, and molecular electronics . 26. A product prepared by a process comprising: (a) selecting carbon nanotubes; and (b) reacting the carbon nanotubes with a diazo compound to generate derivative carbon nanotubes. 27. A monolayer nanotube solution prepared by a method comprising: (a) derivatized single-walled carbon nanotubes, wherein the derivatized carbon nanotubes are derived from diazo compounds; (b) a solvent, wherein the derivatized carbon nanotubes are dispersed in the solvent. 28. A product comprising: (a) derivatized carbon nanotubes, and; (b) A molecule covalently bonded to said derivatized carbon nanotube, wherein said molecule is operable in a capability selected from molecular switches, molecular wires, and molecular electronics. 29. The method of claim 28, wherein the derivatized carbon nanotubes are derivatized single-walled carbon nanotubes. 30. The method of claim 29, wherein the molecule is a molecular wire, wherein the molecular wire is operatively connected to a molecular electronic component. 31. The method of claim 29, wherein the molecular wire comprises an oligo(phenyleneethynylene) molecular wire. 32. A method of derivation of carbon nanotubes, said method comprising: (a) select single-layer carbon nanotube components; (b) immersing the group of carbon nanotubes in a solution containing a diazo compound; and (c) applying a potential to the nanotube assembly to electrochemically react with the diazo compound. 33. The method of claim 32, wherein the carbon nanotubes are single-walled carbon nanotubes. 34. The method of claim 33, wherein the carbon nanotube assembly is a carbon nanotube intersection structure. 35. The method of claim 33, further comprising preparing the assembly by flowing a fluid over the patterned surface. 36. The method of claim 33, further comprising attaching a functionalized molecule to the nanotube assembly. 37. The method of claim 36, wherein the functionalized molecules comprise molecules that function in a capability selected from molecular switches and molecular wires. 38. The method of claim 33, further comprising operatively linking the molecular electronic component to the nanotube. 39. A product prepared by a process comprising: (a) select single-layer carbon nanotube components; (b) immersing the group of carbon nanotubes in a solution containing a diazo compound; and (c) applying a potential to the nanotube assembly to electrochemically react with the diazo compound. 40. A method of preparing a polymeric material, said method comprising: (a) conducting a derivation reaction between the carbon nanotube and the functional part to generate a derivative carbon nanotube, characterized in that the functional part is derivatized onto the carbon nanotube by using a diazo compound; (b) dispersing the derivatized carbon nanotubes in a polymer. 41. The method of claim 40, wherein the carbon nanotubes are single-walled carbon nanotubes. 42. The method of claim 41, wherein the functional moiety is chemically bonded to the polymer. 43. The method of claim 41, wherein the functional moiety is not chemically bonded to the polymer. 44. The method of claim 41, wherein the functional moiety is removed after the dispersing step. 45. The method of claim 44, wherein the removing step comprises heating the dispersion of the derivatized nanotubes and the polymer to at least about 250°C. 46. The method of claim 41, wherein the functional moiety is operable to react with a curing agent. 47. The method of claim 46, wherein the polymer includes a curing agent. 48. The method of claim 6, wherein the curing agent is dispersed in the dispersion of the derivatized carbon nanotubes and the polymer. 49. The method of claim 46, wherein the curing agent comprises an agent selected from the group consisting of diamines, polythiols, and phenolic substances. 50. The method of claim 41, wherein the functional moiety is operable to react with the epoxy moiety. 51. The method of claim 50, wherein the polymer comprises an epoxy moiety. 52. The method of claim 46, further comprising curing the derivatized carbon nanotubes and the polymer dispersion. 53. The method of claim 50, further comprising curing the derivatized carbon nanotubes and the polymer dispersion. 54. A polymeric material, said product comprising: (a) derivatized carbon nanotubes, characterized in that the derivatized carbon nanotubes include a portion of a diazo compound, and (b) A polymer, characterized in that the derivatized carbon nanotubes are dispersed in the polymer. 55. The method of claim 54, wherein the carbon nanotubes are single-walled carbon nanotubes. 56. The method of claim 54, wherein the derivatized carbon nanotubes and the polymer are crosslinked. 57. A method of preparing a polymeric material, the method comprising: (a) carbon nanotubes and functional groups carry out derivatization reaction, generate derived carbon nanotubes, it is characterized in that, (i) derivatizing said functional groups onto carbon nanotubes using a diazo compound; and (ii) the functional group can polymerize; and (b) subjecting the derivatized carbon nanotubes to a polymerization reaction such that the polymer grows from the functional groups. 58. The method of claim 57, wherein the carbon nanotubes are single-walled carbon nanotubes. 59. The method of claim 58, wherein said polymerizing step comprises a technique selected from free radical, cationic, anionic, polycondensation, ring opening, metathesis, or ring opening-metathesis (ROMP) polymerization. 60. A polymer prepared by a process comprising: (a) carbon nanotubes and functional groups carry out derivatization reaction, generate derived carbon nanotubes, it is characterized in that, (i) derivatizing said functional groups onto carbon nanotubes using a diazo compound; and (ii) the functional group can polymerize; and (b) subjecting the derivatized carbon nanotubes to a polymerization reaction to grow polymers from the functional groups. 61. The method of claim 60, wherein the carbon nanotubes are single-walled carbon nanotubes. 62. The method of claim 61, wherein said polymerizing step comprises a technique selected from free radical, cationic, anionic, polycondensation, ring opening, metathesis, or ring opening metathesis (ROMP) polymerization.

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