Investigation of Hybrid Conjugated/Nonconjugated Polymers for Sorting of Single-Walled Carbon Nanotubes

Structure-selectivity relationships between conjugated polymer backbone structure and enriched semiconducting carbon nanotube dispersions remain unclear. A significant focus has been on the structure of the aromatic monomer incorporated into the conjugated polymer backbone, particularly with respect to derivatives of fluorene, thiophene, and carbazole. Less attention has been given to challenging the necessity of complete backbone conjugation in preparing samples of enriched semiconducting carbon nanotubes. Here, we synthesize and study a series of polymer backbone structures containing nonconjugated flexible linkers with lengths of 3-12 carbon atoms and incorporation percentages of 5-50%. We prepare nanotube dispersions with HiPCO starting material and characterize the dispersions using UV-vis-NIR, Raman, and fluorescence spectroscopy. We that at an optimized alkyl spacer length (six carbon atoms) and incorporation percentage (25%) an enriched sample of semiconducting carbon nanotubes can be prepared in THF, showing that complete polymer conjugation is not necessary for nanotube sorting. Furthermore, we demonstrate that these polymers are efficient at dispersing higher average diameter plasma torch carbon nanotubes in both THF and toluene and that enriched, concentrated dispersions of semiconducting tubes can be achieved in toluene.