Understanding the Selection Mechanism of the Polymer Wrapping Technique toward Semiconducting Carbon Nanotubes

• Published in: Small methods Vol. 2; no. 4
• Main Authors: Salazar‐Rios, Jorge Mario, Talsma, Wytse, Derenskyi, Vladimir, Gomulya, Widianta, Keller, Tina, Fritsch, Martin, Kowalski, Sebastian, Preis, Eduard, Wang, Ming, Allard, Sybille, Bazan, Guillermo Carlos, Scherf, Ullrich, dos Santos, Maria Cristina, Loi, Maria Antonietta
• Format: Journal Article
• Language: English
• Published: 10-04-2018
• Subjects: dispersion yield; field‐effect transistors; polymer wrapping; single‐walled carbon nanotubes; sorting ability
• ISSN: 2366-9608; 2366-9608
• DOI: 10.1002/smtd.201700335

Noncovalent functionalization of single‐walled carbon nanotubes (SWNTs) using π‐conjugated polymers has become one of the most effective techniques to select semiconducting SWNTs (s‐SWNTs). Several conjugated polymers are used, but their ability to sort metallic and semiconducting species, as well as the dispersions yields, varies as a function of their chemical structure. Here, three polymers are compared, namely, poly[2,6‐(4,4‐bis‐(2‐dodecyl)‐4H‐cyclopenta[2,1‐b;3,4b′]dithiophene)‐alt‐4,7(2,1,3‐benzothiadiazole)] (P12CPDTBT), poly(9,9‐di‐n‐dodecylfluorenyl‐2,7‐diyl) (PF12), and poly(3‐dodecylthiophene‐2,5‐diyl) (P3DDT) in their ability to select two types of carbon nanotubes comprising small (≈1 nm) and large (≈1.5 nm) diameters. P12CPDTBT is a better dispersant than PF12 for small diameter nanotubes, while both polymers are good dispersants of large diameter nanotubes. However, these dispersions contain metallic species. P3DDT, instead presents the best overall performance regarding the selectivity toward semiconducting species, with a dispersion yield for s‐SWNTs of 15% for small and 21% for large diameter nanotubes. These results are rationalized in terms of electronic and chemical structure showing that: (i) the binding energy is stronger when more alkyl lateral chains adsorb on the nanotube surface; (ii) the binding energy is stronger when the polymer backbone is more flexible; (iii) the purity of the dispersions seems to depend on a strong polymer–nanotube interaction.
Single‐walled carbon nanotubes of different diameters are sorted using three different conjugated polymers. The results are rationalized in terms of electronic structure calculations on model systems and geometrical parameters governing the wrapping process. The calculated binding energies are stronger when more alkyl lateral chains adsorb on the nanotube surface, and when the polymer backbone is more flexible.