Effect of Induction on the Dispersion of Semiconducting and Metallic Single-Walled Carbon Nanotubes Using Conjugated Polymers

Despite significant advances in single-walled carbon nanotube (SWNT) synthesis and purification strategies, the separation of metallic and semiconducting SWNTs on a large scale remains a barrier to the realization of many commercial applications. Selective extraction of specific SWNT types by wrapping and dispersion with conjugated polymers has been found effective for semiconducting SWNTs, but structural parameters that dictate selectivity are poorly understood. Here, we report nanotube dispersions with two structurally similar conjugated copolymers, both being poly(fluorene-co-phenylene) derivatives, having comparable degrees of polymerization but differing in the extent of electron donation from functional groups on the phenylene comonomers. It is found that copolymers decorated with electron donating methoxy functionalities lead to predominant dispersion of semiconducting SWNTs, while copolymers decorated with electron withdrawing nitro functionalities bias the dispersion toward metallic SWNTs. Differentiation of semiconducting and metallic SWNT populations was carried out by a combination of UV-vis-NIR absorption spectroscopy, Raman spectroscopy using multiple excitation wavelengths, and fluorescence spectroscopy. These results provide new insight into polymer design features that dictate preferential dispersion of specific SWNT types.