Reductive dissolution of supergrowth carbon nanotubes for tougher nanocomposites by reactive coagulation spinning

Abstract

Long single-walled carbon nanotubes, with lengths >10 μm, can be spontaneously dissolved by stirring in a sodium naphthalide N,N-dimethylacetamide solution, yielding solutions of individualised nanotubide ions at concentrations up to 0.74 mg mL. This process was directly compared to ultrasonication and found to be less damaging while maintaining greater intrinsic length, with increased individualisation, yield, and concentration. Nanotubide solutions were spun into fibres using a new reactive coagulation process, which covalently grafts a poly(vinyl chloride) matrix to the nanotubes directly at the point of fibre formation. The grafting process insulated the nanotubes electrically, significantly enhancing the dielectric constant to 340% of the bulk polymer. For comparison, samples were prepared using both Supergrowth nanotubes and conventional shorter commercial single-walled carbon nanotubes. The resulting nanocomposites showed similar, high loadings (ca. 20 wt%), but the fibres formed with Supergrowth nanotubes showed significantly greater failure strain (up to ∼25%), and hence more than double the toughness (30.8 MJ m), compared to composites containing typical ∼1 μm SWCNTs.

Charged Carbon Nanomaterials: Redox Chemistries of Fullerenes, Carbon Nanotubes, and Graphenes

“…148,149 Simple stirring of ultralong nanotubides can lead to sufficient breakage that individualized nanotubide solutions form conveniently, while still retaining greater lengths than conventional dispersion methods. 87 Dissolution of ultralong SWCNTs through dissociative protonation has also demonstrated individualization (albeit only at lower concentrations, 311 ca. 50 ppm).…”

“…The charging of the nanomaterial is typically unaffected by the aspect ratio, aside from extremely short length scales where edge effects may dominate; however, the dissolution kinetics have recently been proposed to be inversely proportional to their aspect ratio. 87,150 The aspect ratio has a significant effect on the phase behavior of the subsequent solution (section 5.3). of graphite to sulfuric acid; 153 this acid treatment route subsequently also led to the discovery 154 of graphite oxide in 1859.…”

“…Although certain systems dissolve completely, spontaneously, yields are maximized, or at least accelerated, by modest agitation; simple slow stirring is usually sufficient. Particularly long or entangled SWCNT samples may require extended or more vigorous stirring, 87 sufficient to break the longer, more susceptible species. In the absence of agitation, partial dissolution (for example, at lower degrees of charging) may be selective due to both thermodynamic and kinetic effects (section 6).…”

“…182 This residual charge does not occur for fullerides, as the first functionalization forms a functionalized fulleride (RC 60 n− ) which is typically more reactive than the more highly charged parent fulleride (C 60 (n+1)− ); since functionalized fullerides have lower symmetry and more localized charges, they act as strong nucleophiles which react preferentially until the charge is exhausted. 343 Some reagents with particularly high reduction potentials are known to react with nanotubide, 87,143,367,368 most notably alkyl chlorides (ca. −2.8 to −3.1 V vs SHE, 369 greater than sodium, −2.71 V), which are unlikely to undergo direct reduction from the CCN, indicating that the current understanding of the grafting mechanism is incomplete.…”

Reactive coagulation of single-walled carbon nanotubes for tougher composites – Solution processing and assembly

“…In this approach, the SWCNTs are wrapped in polymer, as evidenced by their lack of electrical conductivity and high composite dielectric constant, even at high loadings. 5 The composite mechanical properties can be modulated by SWCNT selection: longer SWCNTs give higher strain-to-failure and more crystalline nanotubes provide higher strength. Nevertheless, while the mechanical properties of these composites are higher than nanotubide-derived pure SWCNT fibres, their performance is limited by poor processing and has significant scope for improvement.…”