Functionalization of polyfluorene‐wrapped carbon nanotubes using thermally cleavable side‐chains

Abstract The length and nature of side‐chains in conjugated polymer‐wrapped carbon nanotubes can impact their conductivity. We investigate functionalization of polyfluorene‐single‐walled carbon nanotubes (SWNT's) using cleavable side‐chains that are removable post‐processing. The triethylene glycol side‐chains contain a thermally cleavable carbonate linker. Upon heating the films to 170 °C, the conductivity increased, reaching a plateau of (2.0 ± 0.1) × 10 −2  S/m after 16 h, compared to (1.0 ± 0.2) × 10 −3  S/m for the control sample. UV–Vis–near‐infrared (NIR) and Raman spectroscopy show well‐dispersed SWNT samples and confirm that the heating treatment did not damage the nanotubes. Functionalization using longer polyethylene glycol side‐chains was also investigated. After heating, cleavage of the longer chains resulted in conductivity of (8.2 ± 1.6) × 10 −4  S/m compared to (8.1 ± 1.4) × 10 −5  S/m for the control. UV–Vis–NIR and Raman spectroscopy showed well‐dispersed SWNT samples and confirmed that the nanotubes were not damaged. Finally, we investigate dispersions in triethylene glycol monomethyl ether and tetraethylene glycol dimethyl ether, generally deemed “green” solvents. Polymer‐SWNT complexes functionalized with shorter side‐chains did not form stable dispersions, resulting in precipitation of the nanotubes upon standing for a few minutes after the removal of tetrahydrofuran, while complexes functionalized with longer side‐chains formed stable dispersions.