Supramolecular complexes of single walled carbon nanotubes with conjugated polymers

We have synthesized a series of conjugated polymers, including poly[(2,7-(9,9-dioctylfluorene)-alt-2,7-(9,9-didodecylfluorene)] (PF), poly[(2,7-(9,9-dioctylfluorene)-alt-2,5-(3-dodecylthiophene)] (PFT), and poly(3-dodecylthiophene) (PT). Non-covalent functionalization of single walled carbon nanotubes (SWNTs) with these polymers can impart good solubility to nanotubes in a number of organic solvents, including THF, dichlorobenzene, chloroform, and toluene. Solution and solid-state characterization of the resulting polymer–SWNT composites are described, including UV-Vis absorption and Raman spectroscopy. It was found that the UV-Vis absorption maximum of the polymers was red-shifted in their corresponding composites due to the planarization of the polymer backbone following adsorption upon the SWNT surface. Polymer–SWNT complexes also exhibited good solution stability at elevated temperature in THF and dichlorobenzene, with no significant SWNT sedimentation observed at elevated temperatures. Both UV-Vis absorption and Raman spectroscopy results indicated that the interaction of PT with the nanotubes was different from those of PF and PFT, suggesting that the choice of aromatic ring in the polymer structures plays an important role in the supramolecular complex formation with carbon nanotubes.