Pillar[5]arene Decorated Single-Walled Carbon Nanotubes

Abstract

Control of single-walled carbon nanotube dispersion properties is of substantial interest to the scientific community. In this work, we sought to investigate the effect of a macrocycle, the pillar[5]arene, on the dispersion properties of a polymer-nanotube complex. Pillar[5]arenes are a class of electron-rich macrocyclic hosts capable of forming inclusion complexes with electron-poor guests, such as alkyl nitriles. A hydroxyl-functionalized pillar[5]arene derivative was coupled to the alkyl bromide side-chains of a polyfluorene, which was then used to coat the surface of single-walled carbon nanotubes. Differentiation of semiconducting and metallic SWNT species was analyzed by a combination of UV-Vis-NIR, Raman, and fluorescence spectroscopy. Raman spectroscopy confirmed that the concentrated nanotube dispersion produced by the macrocycle-containing polymer was due to well-exfoliated nanotubes, rather than bundle formation. The polymer-nanotube dispersion was investigated using 1H-NMR spectroscopy, and it was found that host-guest chemistry between pillar[5]arene and 1,6-dicyanohexane occurred in the presence of the polymer-nanotube complex. Utilizing the host-guest capability of pillar[5]arene, the polymer-nanotube complex was incorporated into a supramolecular organogel.