Degradable Fluorene- and Carbazole-Based Copolymers for Selective Extraction of Semiconducting Single-Walled Carbon Nanotubes

Among the solution-based purification methods of as-produced single-walled carbon nanotubes (SWCNTs), conjugated polymer sorting is one of the most promising approaches to obtain semiconducting SWCNTs (s-SWCNTs) with high purity. In order to meet the demand for pure polymer-free s-SWCNTs after polymer wrapping, we synthesized several degradable fluorene- and carbazole-based copolymers for selective extraction of s-SWCNTs. The copolymers are interlinked by imine bonds, and thus, the cleavage can be easily accomplished by acid treatment. The polymer/SWCNT complex dispersions were prepared with as-produced HiPco SWCNTs in toluene and characterized with absorption, photoluminescence excitation and emission mapping, and Raman spectroscopy. Among the synthesized polyimines, fluorene-carbazole copolymers show extremely high separation yield toward s-SWCNTs and high separation purity, while the fluoreneâEuro"fluorene and fluorene-p-phenylene copolymers show lower yield but higher selectivity to s-SWCNT with specific pairs of (n,m) indices. Quantitative removal of the polymer after acid-triggered degradation was confirmed by X-ray photoelectron spectroscopy. Moreover, the released dispersant-free s-SWCNTs can be further rewrapped by different polymers. Our results pave the way toward the use of dispersant-free semiconducting carbon nanotubes (CNTs) to develop the next generation of CNT devices.