Engineering the Structural Topology of Pyrene-Based Conjugated Polymers for the Selective Sorting of Semiconducting Single-Walled Carbon Nanotubes

Abstract

To enable the application of semiconducting single-walled carbon nanotubes (sc-SWNTs) in advanced technologies, the SWNT chiralities must be sorted from the mixture of as-synthesized SWNTs. Interestingly, conjugated polymers have the ability to sort sc-SWNTs with different chiralities selectively, and this sorting effect is dependent on the polymer backbone structure. However, design principles for polymer backbones that allow the selective separation of desired SWNT chiralities are still unknown. To investigate the relationship between the polymer backbone structure and the sorting effect systematically, we used three pyrene moieties to prepare different structural topologies of diketopyrrolopyrrole (DPP)-based polymers. As expected, the backbone of three synthesized polymers is gradually linearized from P(1,8-pyDPP) to P(1,6-pyDPP) and P(2,7-pyDPP). Further, these polymers successfully enrich sc-SWNTs of the high-pressure carbon monoxide (HiPco) SWNTs by using an efficient washing process. We obtained high-quality sc-SWNT solutions without impurities or excess polymer by using P(1,6-pyDPP) because of the good dispersibility arising from the slightly kinked backbone. It was also found that the very kinked backbone of P(1,8-pyDPP) increased the preference for specific diameters of SWNTs, whereas the linear backbone of P(2,7-pyDPP) was favorable for the sorting of sc-SWTNs with large diameters. We believe that our findings regarding the polymer-backbone-topology-dependent sorting ability for sc-SWNTs offer important fundamental information on the structural design of conjugated polymers.