Multiscale modelling of Carbon nanotubes

Abstract

A comprehensive understanding of nanotube materials requires the ability to link different carbon nanotube models, which were developed to work at different length scales. Here we describe the mapping of a molecular dynamics (MD) model for single-wall carbon nanotubes onto a wormlike chain. This mapping employs a mode analysis of the bending fluctuations of the nanotube, similar to those used in experiments [1]. The essence of this mapping is to find an appropriate bending stiffness for the wormlike cha in in order to represent the nanotube on a coarsened scale. We find that this mapping will only work well, if the wavelength probing the nanotube stiffness is sufficiently large. For single-wall (9,9) armchair nanotubes vibration modes with node distances of 3 nm underestimate the long wavelength limit of the bending constant by about 50%. This mismatch tends to increase for tubes with larger radii.

Size‐Dependence and Elasticity of Liquid‐Crystalline Multiwalled Carbon Nanotubes

“…Apparently, this is reminiscent of liquid-crystalline polymers. Nevertheless, because of the different scales and nature of their rigidity between the nanotube crystals and polymeric chains, [28][29][30] the Frank elastic constants of nanotubes and their functions of nanotube rigidity and dimensions are worthwhile to be further studied. In summary, hierarchically ordered liquid-crystalline structures of multiwalled carbon nanotubes are revealed to show size dependence, with the elastic deformations of individual nanotubes taking part if their size lies on the border between the micro-and nanometer levels.…”

Mesogenicity Drives Fractionation in Lyotropic Aqueous Suspensions of Multiwall Carbon Nanotubes

“…This process can then be repeated successively to give further enhancement of the mesogenicity of the species forming the liquid crystalline phase. As the length of carbon nanotubes is considered to be exceptionally high, fractionation is possible over a considerable nanotube length range within which the aspect ratios are greater than 100:1 . This fractionation would then allow nanotubes to be purified on the basis of their affinity for the liquid crystalline phase, which is their mesogenicity, to produce monodispersed samples, which would be of significant scientific and technological value.…”

“…As the length of carbon nanotubes is considered to be exceptionally high, fractionation is possible over a considerable nanotube length range within which the aspect ratios are greater than 100:1. 27 This fractionation would then allow nanotubes to be purified on the basis of their affinity for the liquid crystalline phase, which is their mesogenicity, to produce monodispersed samples, which would be of significant scientific and technological value. Furthermore, the use of nanotubes, which can be directly observed in the scanning electron microscope in dried samples, adds scientific understanding to lyotropic liquid crystals and their phase diagram.…”

Carbon Nanotube Synthesis and Organization

“…They are, however, very stiff compared with even the stiffest polymer molecules. Computational modeling [117] indicates that the persistence length of even a small-diameter single-wall carbon nanotube (7,7) is some tens of micrometers, which would make it some 100 times stiffer than DNA. While such a value may be surprising, it should be remembered that a thin-walled tube is amongst the stiffest, per unit mass, of all engineering structures, and in the case of carbon nanotubes bending requires the stretching and compression of the strong carbon-carbon bonds.…”