Morphology and dispersion of polycarbazole wrapped carbon nanotubes

Using MM3 force-field simulations in combination with optical measurements, we investigate the morphology and dispersion of a variety of single-walled carbon nanotubes (SWNTs) non-covalently functionalized by carbazole polymers. Our results elucidate that isomer types of poly-carbazoles together with their length govern the morphology of carbazole-SWNT hybrids and, hence, their dispersion and bundling properties. The pi-pi stacking between the carbazole and the SWNT results in a stable carbazole-SWNT hybrid complex with the SWNT-carbazole interaction increasing with a decrease in the polymer length. All oligocarbazoles preferentially bind to larger diameter SWNTs with the strongest interactions observed for the hybrids with 2,7-isomers. While short oligocarbazoles cover only one side of the tube, long 2,7-isomers tend to gradually coil around the entire tube. In contrast, 3,6- and 2,7-3,6-oligocarbazoles irregularly bunch together on a small area of the tube. The small size of carbazole oligomers and their localization on one side of the nanotube prevents tube unbundling, and leads to photoluminescence quenching in SWNTs functionalized by 2,7-3,6-oligocarbazoles.