Solvation of carbon nanotubes by aniline calculated with density functional tight binding

The poor solubility of carbon nanotubes in aromatic solvents is a well known issue. This work is concerned with the fundamentals of the dissolution process of carbon nanotubes. Based on previous studies about adsorption of small aromatics on carbon nanotubes, different arrangements and different numbers of aniline molecules on single walled zigzag and armchair nanotubes are investigated by ab initio density functional based tight binding method. Thereby adsorption energies and distances are obtained. These are compared with results of nanotube bundles. Finally a possible reaction process is formulated and potential curves for different arrangements are calculated. The results of our study are consistent with a low solution ability of small aromatics with respect to carbon nanotubes. Even if insertion of aniline into nanotube bundles is possible, thermal motion of room temperature would squeeze out the aniline. For better solvation the solvents must have larger pi systems or adsorption enhancing substituents.