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Molecular Mechanics Calculations of the Thermodynamic Stabilities of Polymer/Carbon Nanotube Composites

Published

Author(s)

S I. Stoliarov, Marc R. Nyden

Abstract

The formation of the nanocomposite was analyzed in terms of a simple path in which the nanotubes are exfoliated from a bundle and dispersed in a distorted polymer with cylindrical cavities to accommodate the nanotubes. From this perspective, the energy of mixing is the difference between the energy required to exfoliate the nanotubes from a bundle ( ) and the energy needed to extract the nanotubes from the polymer matrix relative to the relaxed polymer without any nanotubes (i.e., ). These energy components were evaluated by performing molecular mechanics calculations on individual, localized models representing the polymer, nanotube bundles, nanotube-polymer agglomerates, and the separated nanotubes. This method was applied to polystyrene/CNT composites and the factors that determine their thermodynamic stability were identified.To a first approximation, the interaction energies (per unit surface area of the nanotubes) were shown to be independent of the lengths, but strongly dependent on the diameters of the component nanotubes. On this basis, it was determined that a thermodynamically stable nanocomposite could be obtained by mixing CNTs with diameters greater than about 14.5 nm in polystyrene. This may explain why it is so difficult to obtain good dispersion of SWCNTs in PS, since they rarely grow to have diameters greater than about 3 nanometers. On the other hand, since the diameters of MWCNTs typically exceed 10 nm, we would expect them to disperse much better than SWCNTs in polystyrene.
Citation
Molecular Mechanics Calculations of the Thermodynamic Stabilities of Polymer/Carbon Nanotube Composites
Publisher Info
Book Chapter Nano Fire Retardants,

Keywords

carbon nanotubes, fire retardants, free energy of mixing, molecular mechanics, polymer/nanotube composites

Citation

Stoliarov, S. and Nyden, M. (2021), Molecular Mechanics Calculations of the Thermodynamic Stabilities of Polymer/Carbon Nanotube Composites, Book Chapter Nano Fire Retardants, (Accessed May 29, 2024)

Issues

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Created October 12, 2021