Removable and Recyclable Conjugated Polymers for Highly Selective and High-Yield Dispersion and Release of Low-Cost Carbon Nanotubes.

High-purity semiconducting single-walled carbon nanotubes (s-SWNTs) with little contamination are desired for high-performance electronic devices. Although conjugated polymer wrapping has been demonstrated as a powerful and scalable strategy for enriching s-SWNTs, this approach suffers from significant contaminations by polymer residues and high cost of conjugated polymers. Here, we present a simple but general approach using removable and recoverable conjugated polymers for separating s-SWNTs with little polymer contamination. A conjugated polymer with imine linkages was synthesized to demonstrate this concept. Moreover, the SWNTs used are without prepurifications and very low cost. The polymer exhibits strong dispersion for large-diameter s-SWNTs with high yield (23.7%) and high selectivity (99.7%). After s-SWNT separation, the polymer can be depolymerized into monomers and be cleanly removed under mild acidic conditions, yielding polymer-free s-SWNTs. The monomers can be almost quantitatively recovered to resynthesize polymer. This approach enables isolation of "clean" s-SWNTs and, at the same time, greatly lowers costs for SWNT separation.