Degradable Conjugated Polymers: Synthesis and Applications in Enrichment of Semiconducting Single‐Walled Carbon Nanotubes

Abstract

Polymers which enrich semiconducting single‐walled carbon nanotubes (SWNTs) and are also removable after enrichment are highly desirable for achieving high‐performance field‐effect transistors (FETs). We have designed and synthesized a new class of alternating copolymers containing main‐chain fluorene and hydrofluoric acid (HF) degradable disilane for sorting and preferentially suspending semiconducting nanotube species. The results of optical absorbance, photoluminescence emission, and resonant Raman scattering show that poly[(9,9‐dioctylfluorenyl‐2,7‐diyl)‐alt‐co‐1,1,2,2‐tetramethyl‐disilane] preferentially suspends semiconducting nanotubes with larger chiral angle (25°–28°) and larger diameter (1.03 nm–1.17 nm) (specifically (8,7), (9,7) and (9,8) species) present in HiPCO nanotube samples. Computer simulation shows that P1 preferentially interacts with (8,7) (semiconducting) over (7,7) (metallic) species, confirming that P1 selects larger diameter, larger chiral angle semiconducting tubes. P1 wrapped on the surface of SWNTs is easily washed off through degradation of the disilane bond of the alternating polymer main chain in HF, yielding “clean” purified SWNTs. We have applied the semiconducting species enriched SWNTs to prepare solution‐processed FET devices with random nanotube network active channels. The devices exhibit stable p‐type semiconductor behavior in air with very promising characteristics. The on/off current ratio reaches up to 15 000, with on‐current level of around 10 μA and estimated hole mobility of 5.2 cm2 V−1 s−1.

Semiconducting single-walled carbon nanotubes sorting with a removable solubilizer based on dynamic supramolecular coordination chemistry

“…The Raman spectra provided proof of the separation of the met-and sem-SWNTs [50][51][52] . For the HiPco-produced SWNTs, based on the Kataura plot 53,54 , we can estimate the ratio of the sem-or met-SWNTs using the RBM region in the Raman spectra measured by excitation at 633 nm, which is a widely used method 31,36,43,55 . Compared with the spectrum of the as-produced SWNTs (black line in Fig.…”

“…1). Mayer and coworkers 42 and Chan-Park and coworkers 43 reported the use of degradable PFOalternating copolymers, with a photocleavable or acid-sensitive moiety, to irreversibly cleave the wrapping polymers in order to remove them from the composites. Although they could obtain the sem-SWNTs as bundles, the purity of the sem-SWNTs was rather low and complete removal of the wrapping polymer was not discussed.…”

Sorting Semiconducting Single‐Walled Carbon Nanotubes by Water‐Soluble Polyfluorene Assisted Electrophoresis and Its Application in Field‐effect Transistors

“…Besides, our group has researched the enrichment of s-SWNTs by degradable polyfluorene derivatives as well. [26] Based on the above researches, we found a promising separation method to obtain high purity of s-SWNTs by using water-soluble polyfluorene assisted agarose gel electrophoresis. There are two main factors for this effective method.…”

Sorting Semiconducting Single-Walled Carbon Nanotubes and Using Them as Random Network of Field-Effect Transistors

“…The di®erent colors represent the on-o® ratio of each device. Compared with pristine HiPco, which has a very low on-o® ratio (in the range of 1 to 10) as measured in our previous study, 43 the devices, prepared as described above from sorted SWCNTs, exhibit high values of on-o® ratio and e®ective mobility. Moreover, it was found that very sparsē lms (1 to 4 SWCNT m À2 ) do not form su±ciently conductive paths to yield measurable on-state current.…”

“…In our previous research, 43 we had found that the residual impurity on the surface of sorted SWCNTs increases tube/tube contacts but reduces carrier mobility, thus limiting the maximum current and lowering the on-o® ratio. This problem can be eliminated by cleaning the surface of SWCNTs.…”