Single-walled Carbon Nanotubes In Organic Solvents Research Articles

Doping-Dependent Energy Transfer from Conjugated Polyelectrolytes to (6,5) Single-Walled Carbon Nanotubes

Conjugated polymers exhibit strong interactions with single-walled carbon nanotubes (SWNTs). These enable the selective dispersion of specific semiconducting SWNTs in organic solvents and polymer-m...

Composites of Functional Poly(phenylacetylene)s and Single-Walled Carbon Nanotubes: Preparation, Dispersion, and Near Infrared Photoresponsive Properties

To explore poly(phenylacetylene) (PPA) deriva- tives as the dispersing agent of single-walled carbon nanotubes (SWNTs), we synthesized a new series of side chain PPAs (denoted as PPA-m, m = 2, 1, 0). The side chains of PPA-m bear a soluble 3,4,5-tris(octyloxy)phenyl moiety at the end, and a biphenyl (m = 2), a phenyl (m = 1), or no phenyl ring (m =0 ) in the middle linked to the PPA main-chain through an ether linkage. All the three PPA-ms can efficiently disperse SWNTs in organic solvents forming stable SWNTs/PPA-m composites. The composites were characterized by microscopy method, absorbance and photoluminescence spectroscopy. Quantitative analysis shows that there is a tendency for PPA-m to preferentially disperse SWNTs with large diameters in tetrahydrofuran and toluene when compared with the normally used surfactant of sodium dodecyl sulfate. The effective interactions between PPA-m and SWNTs should be ascribed to the helical wrapping of the PPA-m backbone on SWNTs and the π−π interactions between the phenyl groups and SWNTs. The long alkyl tails on the side-chains also prevent individual SWNTs from reaggregation. Additionally, the near-infrared (nIR) photoresponsive electrical conductivity of the SWNTs/PPA-2 composite is measured, indicating a 12% increase of the photocurrent upon the nIR irradiation, which is greater compared with that of the reported pure SWNTs film.

Press-transfer optically transparent electrodes fabricated from commercial single-walled carbon nanotubes

A simple method for the fabrication of optically transparent electrodes (OTE) from commercial single-walled carbon nanotubes (SWCNT) is presented. We disperse SWCNT in organic solvents, avoiding surfactants. Films obtained by filtering are transferred to non-conductive polymer substrates only by pressure, avoiding the chemical removing of the filter. The electro-optical properties of the electrodes have been studied and optimized using an experimental design strategy, concluding that both properties depend on the total mass of SWCNT transferred to the support. In general, well-interconnected SWCNT networks yield little differences in the electrochemical behavior. However, it has been observed that electrodes with a high mass of SWCNT produce significant changes in the voltammograms, obtaining unexpected ratios between the anodic and cathodic peak currents. SWCNT-OTE have been used to study the electropolymerization of aniline.

Green tea-aided dispersion of single-walled carbon nanotubes in non-water media: Application for extraordinary reinforcement of nanocomposite fibers

Green tea has recently been reported to be a good dispersant of single-walled carbon nanotubes (SWCNTs) in aqueous media. In the current work, green tea extract powder was examined for dispersion of SWCNTs in organic solvents. Dimethyl sulfoxide (DMSO) was found to be a good solvent of green tea extract for dispersing SWCNTs. A combination of green tea (dispersant)/DMSO (solvent)/polyvinyl alcohol (PVA) (nanotube wrap) was obtained that resulted in the dispersion of SWCNTs almost to individual nanotubes or to very thin nanotube bundles. The reinforcing ability of highly dispersed SWCNTs was explored in a PVA matrix producing PVA-SWCNT gel-spun fibers. Extraordinary reinforcing effects on the tensile and dynamic mechanical properties of the composites were observed by incorporating a minute amount of SWCNTs (∼1 wt% to PVA). The analysis revealed effective stress transfer through the PVA crystalline interfaces surrounding the nanotubes.

Systematic Study of the Dispersion of SWNTs in Organic Solvents

Dispersions of as-produced HiPco single-walled carbon nanotubes (SWNTs) in a series of organic solvents were prepared by dilution with the aid of tip sonication. Mild centrifugation (∼945 g) was carried out to remove large bundles. Atomic force microscopy (AFM) studies revealed that the bundle size decreased as the dispersion was diluted. By measuring the UV−vis−NIR absorption before and after centrifugation as a function of the concentration, the dispersion limit of SWNTs in each solvent can be determined. Correlations between the dispersion limit and solvent solubility parameters, including the Hildebrand solubility parameter and three-dimensional Hansen solubility parameters, are explored, demonstrating that SWNTs are easily dispersed in solvents with Hildebrand solubility parameter range from ∼22−24 MPa1/2 and Hansen polarity component (δP) ∼12−14 MPa1/2. No clear correlation between dispersion limits and the dispersion force (δD) or hydrogen bonding force (δH) are evident. It is found, however, that the degree of dispersion depends critically on sample preparation conditions and in particular sonication time. Increased sonication times increase the amount of SWNTs debundled and solubilized but do not appear to affect the dispersion limit. However, increased sonication also induces discernible changes to the SWNTs themselves and in itself influences their solubility, under which conditions no clear solubility parameters can be determined.

Reinforcing Epoxy Polymer Composites Through Covalent Integration of Functionalized Nanotubes

AbstractStrong interfacial bonding and homogenous dispersion have been found to be necessary conditions to take full advantage of the extraordinary properties of nanotubes for reinforcement of composites. We have developed a fully integrated nanotube composite material through the use of functionalized single‐walled carbon nanotubes (SWNTs). The functionalization was performed via the reaction of terminal diamines with alkylcarboxyl groups attached to the SWNTs in the course of a dicarboxylic acid acyl peroxide treatment. Nanotube‐reinforced epoxy polymer composites were prepared by dissolving the functionalized SWNTs in organic solvent followed by mixing with epoxy resin and curing agent. In this hybrid material system, nanotubes are covalently integrated into the epoxy matrix and become part of the crosslinked structure rather than just a separate component. Results demonstrated dramatic enhancement in the mechanical properties of an epoxy polymer material, for example, 30–70 % increase in ultimate strength and modulus with the addition of only small quantities (1–4 wt.‐%) of functionalized SWNTs. The nanotube‐reinforced epoxy composites also exhibited an increased strain to failure, which suggests higher toughness.

Effect of Amines on Single-Walled Carbon Nanotubes in Organic Solvents: Control of Bundle Structures

We have investigated the control of bundle structures of single-walled carbon nanotubes (SWNTs) in organic solvents using atomic force microscopy (AFM) and transmission electron microscopy (TEM). We have reported herein that organic amines are effective in untangling the bundled SWNTs in N,N-dimethylformamide (DMF). When Bucky paper was sonicated in DMF with 1% organic amine for 1 h, AFM images clearly showed mainly individual SWNTs. The time-dependent TEM observation revealed that the role of amine is to prevent rebundling of SWNTs in organic solvents.