Empirical evaluation of attractive van der Waals potentials for type-purified single-walled carbon nanotubes

Abstract

Van der Waals forces play a critical role in the structure and stability of single-wall carbon nanotube (SWCNT) materials. Thin films assembled from SWCNTs purified by electronic type show particular promise for flexible electronics applications, but mechanical durability remains an unresolved issue. Using transition resonances determined from spectroscopic measurements of typepurified SWCNTs deposited on quartz, coupled with analogous spectroscopic characterization of polydimethylsiloxane (PDMS) substrates, we use the Lifshitz theory of van der Waals dispersion interactions developed by Rajter and co-workers [R. F. Rajter et. al., Phys. Rev. B 76, 045417 (2007)] to examine the influence of electronic type on van der Waals contact potentials in polymer supported nanotube networks. Our results suggest a significantly stronger nanotube-nanotube and nanotube-polymer attraction for the semiconducting SWCNT fractions, consistent with recent measurements of the electronic durability of flexible transparent SWCNT coatings.PACS numbers: 61.48. De, 78.67.Ch, 82.35.Np, 78.20.Bh 2 I. INTRODUCTIONVan der Waals (vdW) forces play a significant role in the structural stability of matter across a broad range of chemistry, physics, and biology. 1-6 They also play a particularly important role in nanotechnology, where they dominate the short-range attraction between nanoparticles and can hinder their dispersion and manipulation. [7][8][9][10][11] For particles lacking a permanent dipole moment, vdW dispersion forces arise solely from small fluctuations in the electromagnetic field -or more precisely, the dielectric permittivity -across the space between the particles, 12,13 which is dominated by the zero-point energy of quantum vacuum fluctuations. The quantum-field nature of such a mundane, ubiquitous and sometimes macroscopic force is quite remarkable, if on occasion not fully appreciated.Single-wall carbon nanotubes (SWCNTs) are nanometer thick tubes of graphene 100 nm to 100 µm in length. They can be either metallic or semiconducting, depending on the chiral vector (n, m) that characterizes the symmetry of rolling a 2D graphene sheet into a hollow tube. 14 They are one of the most studied materials within the realm of modern nanotechnology, with exceptional physical properties that herald the possibility of significant technological potential. 15 The importance of vdW forces in SWCNT materials cannot be overstated. The high aspect ratio and strong anisotropy create potential wells thousands of k B T in depth, but SWCNTs have yet to realize their full potential as mechanical reinforcing agents. This is primarily due to the mechanical failure of interfacial contacts, which are largely governed by vdW forces. Although chemical crosslinking can help mitigate such effects, this often occurs at the expense of the intrinsic SWCNT properties of interest, 16 which can limit the potential impact of applications.Raw nanotube materials typically contain a broad distribution of lengths and a mixture of the two distinct electronic species...

Nonadditivity of nanoparticle interactions

“…Continuum DLP theory (28) accounts for multibody effects, complex electrodynamics of atomic ensembles in the presence of an intervening medium, and retardation of electromagnetic waves through the use of dielectric function determined either experimentally (138) or computationally (139). The application of DLP to NPs has been limited, but a few studies demonstrate a strong mismatch between dispersion forces calculated with and without polarization multibody effects, especially for organic solvents (140) and small particles of few-nanometer size (141).…”

Non-covalent functionalization of single wall carbon nanotubes and graphene by a conjugated polymer

“…[10][11][12][13] In general, polymers can interact with CNTs or graphene via strong covalent 14 or electrostatic interactions, 15 p-stacking, 16,17 hydrogen bonding, 18 or weak van der Waals (vdW) interactions. 19,20 Non-covalent functionalization with conjugated polymers is particularly attractive, because chemical groups are attached without disrupting the bonding network of the CNT, whereas covalent functionalization introduces atomic defects and internal stress, which can deteriorate the mechanical properties. 21 Unique electrical and optical properties have been demonstrated for CNTs interacting with conjugated polymers.…”

Localization and length-scale doubling in disordered films on soft substrates

“…[31] and [32]. Previous studies suggest that as the modulus increases, the yield strain decreases, and typical values of the exponent α are around 2 to 2.5 [31,32,34]. For complex fluids in general, this type of strain dependence has recently been used, for example, to model the nonlinear rheology of power-law gels [35], while analogous yield-strain behavior has been observed in glassy colloids [36].…”

“…These experiments are consistent with a pristine coating that has a remarkably high plateau modulus-reflecting the 1 TPa Young modulus of an individual SWCNT-but a very small yield strain. Compression pushes the SWCNTs into van der Waals bundles perpendicular to the direction of strain, which is the source of the plasticity [34].…”