Degradable conjugated polymers: Synthesis and applications in enrichment of semiconducting single-walled carbon nanotubes

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 mainchain fl uorene and hydrofl uoric 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-dioctylfl uorenyl-2,7-diyl)-alt-co-1,1,2,2-tetramethyldisilane] 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 μ A and estimated hole mobility of 5.2 cm ₂ V ^{- 1} s ^{- 1}.