Binding kinetics and SWNT bundle dissociation in low concentration polymer-nanotube dispersions

Single-wall carbon nanotubes are severely restricted by the fact that they exist in bundles. In addition, their interaction with other materials is poorly understood. In this work a new spectroscopic method is described to measure the ratio of free polymer to nanotube-bound polymer in SWNT/polymer solutions. This ratio is highly nonlinear and can be described by a model based on polymer- nanotube adsorption/desorption kinetics. In combination with the experimental data, this model shows that the nanotube bundles decrease in size as the concentration is reduced. Individual nanotubes are stable at low concentration, as supported by atomic force microscopy data. In addition, the model allows the indirect measurement of the polymer-nanotube binding energy at 1.1 eV per molecule. In principle, this method is generic and can be used to monitor dispersions of any metallic nanomaterials in suitable, luminescent organic solutions.