Selective dispersion of single-walled carbon nanotubes with electron-rich fluorene-based copolymers

We herein report the design and synthesis of novel fluorene-based pi-conjugated copolymers containing electron-donating dithiafulvene (DTF) and pi-extended tetrathiafulvalene (exTTF) repeat units through Suzuki coupling polymerization. The resulting copolymers showed a comparable degree of polymerization and retained the redox activity originating from the DTF and exTTF building blocks. Theoretical modeling studies predicted that these electron-rich copolymers could wrap around individual single-walled carbon nanotubes (SWNTs) via intimate pi-stacking, while experimental results confirmed that the copolymers formed stable polymer-SWNT supramolecular complexes in organic solvents with high selectivity for semiconducting SWNTs. Various spectroscopic and microscopic analyses were conducted to show that the electronic nature of conjugated polymer backbones plays an important role in tuning the binding preference of the polymers for particular types of SWNTs, offering an efficient and selective non-covalent method to sort SWNTs from as-produced mixtures.