Role of Surfactant Molecular Structure On Carbon Nanotube Self Assembly: Insights From Atomistic Simulations

Stabilizing aqueous dispersions of carbon nanotubes mono-dispersed in diameter and chirality remains elusive. Surfactants have proven useful in deploying ultra-centrifugation techniques, but the molecular mechanism responsible for their effectiveness remains not fully understood. Based on a number of recent molecular simulation results, including those from our group, it appears that the morphology of the self-assembled surfactant aggregates on the carbon nanotubes strongly affects the effective potential of mean force between pairs of interacting carbon nanotubes. We will discuss here recent results obtained conducting equilibrium molecular dynamics simulations for systems composed of sodium dodecyl sulfate (SDS), sodium dodecyl benzene sulfonate (SDBS), flavin mononucleotide (FMN), and sodium bis(2-ethylhexyl) sulfosuccinate (AOT). The simulations are conducted at room conditions for different surface coverages on (6,6), (12,12), and (20,20) single walled carbon nanotubes. By comparing the different surfactant structures on the various nanotubes we will attempt to provide insights into the molecular mechanisms that could be used to stabilize aqueous dispersions of carbon nanotubes monodispersed in diameter.