Highly Stable Single‐Walled Carbon Nanotube Sorting by Low Molecular Weight Conjugated Polymer with Hydrogen‐Bonded Polyisoprene

Abstract

The π–π interaction between the conjugated polymer and single‐walled carbon nanotubes (SWCNTs) is the key to dispersion and selection of semiconducting nanotubes. High molecular weight (Mw > 10 000 Da) conjugated moieties usually form the main chain of the copolymers designed for sorting to ensure strong π–π interaction. However, low Mw conjugated polymers are sorting‐ineffective because they do not interact with SWCNTs. Additionally, sorted nanotubes in solution aggregate during storage or at low temperatures, possibly due to loss of wrapping ability of the dispersant, and stability of the sorted solution is rarely reported. Here, the effectiveness of polyisoprene with hydrogen‐bonding to induce superior sorting and solution stability in a low Mw conjugated polymer is demonstrated. A vinyl‐terminated‐poly(9,9‐dioctylfluorene) (vinyl‐PFO, Mw ≈ 4500) copolymerized with polyisoprene with hydrogen‐bond containing pendant; Poly(2[[(Butylamino) carbonyl]oxy]ethyl‐acrylate, can select large‐diameter semiconducting nanotubes (1.17 nm), and the sorted solution remains stable as observed by UV spectroscopy and thin‐film transistors, for over a year and at low temperatures; 4, −20, and −80 °C. Furthermore, solution can fabricate ambipolar transistors with averaged charge carrier mobility; 48 cm2 V–1 s–1 for p‐type, and 32 cm2 V–1 s–1 for n‐type, with retention stability > 6000 s.