METHOD FOR POLYMER REMOVAL FROM SINGLE-WALLED CARBON NANOTUBES

Abstract

Processes for selectively dispersing semi-conducting single-walled carbon nanotubes (sc-SWCNTs) in a solvent. One process comprises adding an amine either: to a conjugated polymer extraction process (CPE) of the sc-SWCNTs; or after the CPE of the sc-SWCNTs, in which the amine partially displaces the conjugate polymer associated with the sc-SWNTs dispersed in the solvent. Another process comprises adding an amine either: to a conjugated polymer extraction process (CPE) of the sc-SWCNTs; or after the CPE of the sc-SWCNTs, with the proviso that the amine excludes EDTA. Also, a process for displacement of a conjugated polymer from the surface of semi-conducting single-walled carbon nanotubes (sc-SWCNTs) dispersed in a solvent, which comprises adding an amine either: to a conjugated polymer extraction process (CPE) of the sc-SWCNTs; or after the CPE of the sc-SWCNTs.

Claims

1. A process for selectively dispersing semi-conducting single-walled carbon nanotubes (sc-SWCNTs) in a solvent, the process comprising adding an amine either: a) to a conjugated polymer extraction process (CPE) of the sc-SWCNTs; or b) after the CPE of the sc-SWCNTs, wherein the amine partially displaces the conjugate polymer associated with the sc-SWNTs dispersed in the solvent.

2. A process for selectively dispersing semi-conducting single-walled carbon nanotubes (sc-SWCNTs) in a solvent, the process comprising adding an amine either: a) to a conjugated polymer extraction process (CPE) of the sc-SWCNTs; or b) after the CPE of the sc-SWCNTs, with the proviso that the amine excludes EDTA.

3. A process for displacement of a conjugated polymer from the surface of semi-conducting single-walled carbon nanotubes (sc-SWCNTs) dispersed in a solvent, the process comprising adding an amine either: a) to a conjugated polymer extraction process (CPE) of the sc-SWCNTs; or b) after the CPE of the sc-SWCNTs.

4. The process of claim 1, wherein in step b), the amine is added to the supernatant from the CPE.

5. The process of claim 1, wherein filtration of the sc-SWCNTs dispersed in the solvent takes less time than filtration of dispersed sc-SWNTs prepared by the CPE without the amine.

6. The process of claim 1, wherein step a) comprises: i) mixing raw single-walled carbon nanotubes (SWCNTs) with a conjugated polymer (CP) and an amine in the solvent to yield a solid phase and a liquid phase; and ii) separating the solid phase from the liquid phase, wherein the liquid phase is enriched with the sc-SWCNTs.

7. The process of claim 1, wherein the amine is a non-functionalized amine.

8. The process of claim 1, wherein the amine is an alkylamine.

9. The process of claim 1, wherein the amine is triethylamine, ethanol amine or pyridine.

10. (canceled)

11. The process of claim 1, wherein the concentration of the amine is from 1 ppm to 0.1% by weight.

12. (canceled)

13. The process of claim 1, wherein the conjugated polymer comprises a polyfluorene.

14. The process according to claim 13, wherein the polyfluorene is a 9,9-dialkyl-substituted polyfluorene or a 9,9-diC.sub.8-36-alkyl-substituted polyfluorene.

15. (canceled)

16. The process according to claim 1, wherein the conjugated polymer comprises a polythiophene.

17. The process according to claim 16, wherein the polythiophene is a 3-alkyl-substituted polythiophene or a 3-C.sub.8-18-alkyl-substituted polythiophene.

18. (canceled)

19. The process according to claim 1, wherein the conjugated polymer comprises a copolymer of 3-C.sub.10-18-alkyl-substituted thiophene with one or more comonomer units, the co-monomer comprising one or more of fluorene, bithiophene, phenylene, bipyridine, carbazole, anthracene, naphthalene or benzothiadiazole.

20. The process according to claim 1, wherein the conjugated polymer has a number average molecular weight greater than about 10,000 Da.

21. (canceled)

22. The process of claim 1, wherein the solvent is a non-polar solvent.

23. The process of claim 1, wherein the solvent comprises an aromatic organic solvent.

24. The process of claim 1, wherein the solvent comprises toluene, benzene, ethyl benzene, xylenes, 10methylnaphtalene or mixtures thereof.

25. (canceled)

26. The process of claim 2, wherein in step b), the amine is added to the supernatant from the CPE.

Description

BRIEF DESCRIPTION OF FIGURES

[0038] FIG. 1 shows UV spectra of supernatant from: a conditioning step, 1st, 2nd, 3rd, 4th, and 5th extraction of a CPE using PFDD; and the re-dispersed solution from the filtration of the combined supernatant of the 3rd, 4th, and 5th extraction (35F).

[0039] FIG. 2 shows UV spectra of a 1750 ml solution obtained from a PFDD extraction process that has been conducted by applying 5 successive extractions.

[0040] FIGS. 3A and 3B show UV spectra of re-dispersed solutions in the presence of difference additives.

[0041] FIG. 4 illustrates the effect of different additives on the PFDD/CET ratio.

[0042] FIG. 5 shows UV spectra of re-dispersed solutions of TEA assisted filtration of the combined supernatant from PFDD extraction.

[0043] FIG. 6 illustrates influence of the TEA concentration on the PFDD/CNT ratio for 100 mL of the supernatant.

[0044] FIG. 7 shows the UV spectrum of the re-dispersed film from TEA assisted filtration after large quantity solvent rinsing.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Materials and Methods

Characterizations

[0045] Absorption spectra were collected on a UV-Vis-NIR spectrophotometer (Cary 5000, Varian) in a wavelength range from 300 to 2100 nm. A double beam mode was used with a pure solvent cuvette placed in the reference channel. Raman spectra were acquired with an InVia Raman microscope (Renishaw), using 514 nm (2.41 eV), 633 nm (1.96 eV), and 785 nm (1.58 eV) laser excitation sources and 50 magnification objective lens. Spectra were recorded in 100-3000 cm-1 region with a resolution of 4 cm-1. PLE mapping was done in a home-made system with a titanium-sapphire laser used as a wavelength tunable excitation with a tuning range from 720-1050 nm.

[0046] For yield and SWCNT concentration measurements, absorption spectroscopy was used. Yield is expressed as the mass percentage of sc-SWCNT in the enriched dispersion relative to the total mass of SWCNTs present in the raw material, which was calculated from thermogravimetric analyses (TGA) analysis. Principally, the yield value can be obtained by comparing the weight of sc-SWCNTs in the final product of the enrichment with the weight of starting raw material. But the final product is polymer wrapped/coated SWCNTs and therefore it is a mixture of polymer and SWCNTs. The polymer content in the final product has to be detected in order to evaluate the sc-SWCNT content. A spectroscopic approach is known in the art (Naumov2011), which appears to be a more convenient method to simultaneously determine both the amount of polymer and sc-SWCNTs in the final product. Therefore, polymer and SWCNT concentration (mg/mL) of the enriched dispersions are calculated from their absorption spectra, and then the yield of the enrichment can be deduced.

Polyfluorene Derivatives

[0047] This example provides details of the preferred conjugated polymers.

[0048] Polyfluorenes with two alkyl groups at 9-position with a length from C.sub.8 to C.sub.18 were prepared by Suzuki reaction adapted from prior art methods (e.g. Ding 2002). The obtained polymers with the basic characterization data are listed in Scheme 1 and Table 1, where Td.sup.1% and Tg were measured from thermogravimetric analyses (TGA) and differential scanning calorimetry (DSC).

##STR00001##

TABLE-US-00001 TABLE 1 Characterization data of polyfuorenes Polymer PFO(C8) PFD(C10) PFDD(C12) PFTD(14) PFOD(C18) Mn 26.7 13.6 21.7 13.4 23.7 (kDa) PDI 2.4 2.7 4.1 3.0 4.2 Tg 136 101 48 40 35 ( C.) Td.sup.1 % 390 380 381 374 382 ( C.)

Example 1: Effect of TEA (Triethylamine) on a Large Scale Enrichment (50 Mg)

[0049] 0.5% TEA was added into the conditioning step (to slightly de-dope nanotubes) of a standard CPE using PFDD as the conjugated polymer. A conditioning step (or pre-extraction) was followed by 5 successive PFDD extractions. The product from these extractions were marked as 0CC (conditioning) 1CC (1.sup.St extraction), 2CC (2.sup.nd extraction), 3CC (3.sup.rd extraction), 4CC (4.sup.th extraction), and 5CC (5.sup.th extraction). FIG. 1 displays the UV spectra of the supernatant from each extraction, with the yield () and the absorption peak ratio () values for each extraction is displayed in the inset. The absorption peak ratio () is defined as the ratio of the integrated area of the M11 and S22 peak envelop over the total area in this region. A high , value reflects a high sc-SWCNT purity. In addition, the UV spectra of the re-dispersed solution from the filtration of 3CC, 4CC, and 5CC (Sample 35F) is also shown. It shows the PFDD/CNT ratio was easily reduced to 0.75 by filtration in the assistant of TEA. It should be noted that the yield of Sample 35F was calculated based on the weight of the film from the filtration.

[0050] FIG. 1 shows that the combined yield (n) of the conditioning step (0CC), the 1.sup.st extraction (1CC) and 2.sup.nd extraction (2CC) is more than double that of a CPE without the amine. However, the yield becomes quickly reduced in the successive extractions and this process results in a similar overall yield (15%) for the 6 total extractions compared to a process without TEA. This result may be due to the low SWCNT content of the raw plasma tube sample, which is about 50%. The sc-SWCNT content in the raw plasma tube sample is about 33%. Therefore, a 15% yield means about half of the sc-SWCNTs (in the original raw plasma tube sample) have been extracted by this process.

[0051] It may be concluded that de-doping the SWCNTs with TEA can significantly promote the yield of the initial extractionhowever, with lower sc-SWCNT purity. Overall, the addition of TEA in the conditioning step does not improve the total combined yield for a process with a set of 6 successive extractions. Therefore, if the goal is to achieve high purity and a high yield, a set of successive PFDD extractions without SWCNT de-doping (without TEA) is recommended. However, for an expedited process in which only one or two extractions are performed, the addition of TEA in a pre-conditioning step, provides a good yield.

[0052] FIG. 1 also shows a very low PFDD content of the sample from filtration (Sample 35F), based on the peak intensities of sample 35F at 385 nm and 938 nm. The PFDD/CNT value becomes only 0.75 after a simple rinsing process. A similar filtration in a standard CPE (i.e. without TEA) resulted in a PFDD/CNT ratio of about 15.0, about 20-fold larger than sample 35F.

Example 2: Effect of Different Amines on the Filtration of the Supernatant from Enrichment by PFDD Extraction

[0053] In another set of experiments, different types of amines together with a strong base (NaOH) and a strong acid (HCl) have been tested for promoting the filtration of the supernatant from enrichment. For this purpose, a PFDD extraction process has been conducted by applying 5 successive extractions to produce 1750 mL of combined supernatant with the UV spectra and the relevant characterization data shown in FIG. 2.

[0054] Seven different 200 ml samples of this solution were set aside, with a different additive added to each sample: none (Control or CTR), water (H.sub.2O), triethylamine (TEA), ethanol amine (EOA), pyridine (Py), NaOH and HCl. The amount of each additive is listed in Table 1. Each solution was then bath sonicated for 10 minutes to ensure good mixing, followed by filtration. The filtrate was rinsed with 10 mL of toluene three times. The composition of the resulting solid was then analyzed by UV spectroscopy.

TABLE-US-00002 TABLE 1 Treatment Condition And Filtration Results Sample Before None H2O NaOH HCl TEA EOA PY W.sub.Base (mg)# 10 10 10 63.6 38.5 49.8 MW (g/mol) 101 61.1 79.1 N.sub.B (mmol)* 0.063 0.063 0.63 0.63 0.63 Time (min) 270 270 600 70 55 160 180 PFDD/CNT 152 2.33 2.92 10.8 1.51 0.80 1.46 1.36 Note: *the usage of the base is designed at the molar ratio of carbon/base of 1:4.5 for amines and 1:0.45 for NaOH. #6.3M NaOH and HCl solution were used.

[0055] The addition of the amine compound resulted in a clear solution, thereby indicating good mixing. However, after 10 mg of the NaOH solution was added into the sc-SWCNT dispersion, a white powder was formed. Sonication turned the solution a bit cloudy. Filtering the resulting solution took extremely long time (10 h). In order to check if this was due to the existence of fine NaOH powder blocking the filtration membrane, the obtained filtration cake was soaked in 30/70 (water/MeOH) solution for 3 hours and then dried and 12/17 of the solid was re-dispersed in 100 mL of toluene and filtered again. It took 180 min to complete, at the same level as the first filtration. The absorption spectrum of the redispersed resulting film showed a high PFDD/CNT ratio, indicating the low filtration speed is due to the high content of polymer which blocked the filtration. Therefore the extremely long filtration time and high PFDD/CNT ratio was due to the NaOH treatment. HCl treatment resulted in broad absorption peaksan indicator of heavy doping of the nanotubes. The PFDD/CNT ratio was at a level similar to that of samples treated with EOA and Py.

[0056] The UV spectra of the re-dispersed films from the filtrations using different additives is shown in FIGS. 3A and 3B, with the PFDD/CNT ratio listed in the inset. The effect of different additives to the PFDD/CNT ratio was also compared in FIG. 4. It can be seen that TEA is the most effective regent in removing the wrapping polymer to result in the lowest PFDD/CNT ratio, On the other hand, addition of NaOH showed a negative effect with an increased PFDD/CNT ratio.

Example 3. Effect of TEA Concentration

[0057] Different amounts of TEA were added to 100 mL samples of combined supernatant, shown in Table 2, and then sonicated for 10 min. The solution was filtered, the filtration film was rinsed with 10 mL of toluene, and then was dispersed in toluene for UV spectroscopy analysis.

TABLE-US-00003 TABLE 2 The effect of TEA usage on the filtration of 100 mL of solution. Sample Before TEA-2 TEA-3 TEA-4 TEA-5 W.sub.Base (mg) 320 60 30 10 N.sub.B (mmol) Time (min) 90 70 60 80 PFDD/CNT 1.8 1.06 0.89 1.19

[0058] FIG. 5 displays the UV spectra of the re-dispersed filtration films with different amounts of TEA used of in the filtration. The influence of the TEA usage on the PFDD/CNT ratio is also shown in FIG. 6, in which 30 mg TEA per 100 mL of the solution (corresponding to a TEA/SWCNT ratio of 4.3:1) gives the best performance in reducing the PFDD/CNT ratio.

Example 4. Limit on the Removal of the Wrapping Polymer by TEA Assisted Filtration and Rinsing

[0059] 63 mg of TEA was added to 200 mL of combined supernatant, sonicated for 10 min and then filtered. The filtration film was then rinsed with 200 mL of toluene 3 times, and then dispersed in toluene. The UV spectrum of the resulting sample is shown in FIG. 7, which indicates a PFDD/CNT ratio of 0.65, which was one of the lowest PFDD/CNT ratios observed.

[0060] Of course, it should be appreciated that the above examples only provide an illustration of the inventive subject matter and should not be deemed limiting. Thus, specific embodiments and applications of methods have been disclosed. It should be apparent to those skilled in the art that many more modifications besides those already described are possible without departing from the inventive concepts herein. The inventive subject matter, therefore, is not to be restricted except in the spirit of the appended claims.

[0061] Moreover, in interpreting both the specification and the claims, all terms should be interpreted in the broadest possible manner consistent with the context. In particular, the terms comprises and comprising should be interpreted as referring to elements, components, or steps in a non-exclusive manner, indicating that the referenced elements, components, or steps may be present, or utilized, or combined with other elements, components, or steps that are not expressly referenced. Where the specification claims refers to at least one of something selected from the group consisting of A, B, C . . . and N, the text should be interpreted as requiring only one element from the group, not A plus N, or B plus N, etc.

REFERENCES

[0062] The contents of the entirety of each of which are incorporated by reference. [0063] Jianfu Ding, Zhao Li, Jacques Lefebvre, Fuyong Cheng, Girjesh Dubey, Shan Zou, Paul Finnie, Amy Hrdina, Ludmila Scoles, Gregory P. Lopinski, Christopher T. Kingston, Benoit Simard, Patrick R. L. Malenfant, Enrichment of large-diameter semiconducting SWCNTs by polyfluorene extraction for high network density thin film transistors, Nanoscale, 2014, 6, 2328-2339. [0064] Jianfu Ding, Zhao Li, Jacques Lefebvre, Fuyong Cheng, Jeffrey L Dunford, Patrick R L Malenfant, Jefford Humes, Jens Kroeger, A hybrid enrichment process combining conjugated polymer extraction and silica gel adsorption for high purity semiconducting single-walled carbon nanotubes (SWCNT), Nanoscale 2015, 7 (38), 15741-15747. [0065] Jianfu Ding, Zhao Li, Fuyong Cheng, Benoit Simard, Patrick R. L. Malenfant, Process for purifying semiconducting single-walled carbon nanotubes, U.S. provisional patent application 61/867,630 and WO 2015024115 A1.