Covalent Attachment of Aromatic Diisocyanate to the Sidewalls of Single‐ and Double‐Walled Carbon Nanotubes

We carried out covalent functionalization of single‐ and double‐walled carbon nanotubes (SWNTs and DWNTs) comparatively by using isocyanate chemistry. The introduction of aromatic diisocyanate on the sidewalls of the tubes was verified by the strong IR peak around 2272 cm–1 arising from the NCO asymmetric stretching mode, by the intensified sp3 peak at 285.2 eV in the C1s photoemission spectra, and by a typical TEM image of the amorphous‐like coating. The suppression of the optical properties in a covalently isocyanate‐functionalized SWNT is due to a breakdown of the van Hove singularities, whereas the strong optical activity in a covalently isocyanate‐functionalized DWNT originates from the geometrically shielded inner tubes. The chemically active isocyanate groups at the end of the phenyl diisocyanate that are covalently attached to the sidewalls of the DWNTs will allow us to utilize isocyanate chemistry in synthesizing functional organic–inorganic hybrid materials as well as high‐performance polymer composites.