Conjugated Polymers with Self‐Immolative Sidechain Linkers for Carbon Nanotube Dispersion

Single‐walled carbon nanotubes (SWNTs) are promising materials for generating high‐performance electronic devices. However, these applications are greatly restricted by their lack of purity and solubility. Commercially available SWNTs are a mixture of semi‐conducting (sc‐) and metallic (m‐) SWNTs and are insoluble in common solvents. Conjugated polymers can selectively disperse either sc‐ or m‐SWNTs and increase their solubility; however, the conductivity of conjugated polymer‐wrapped SWNTs is largely affected by the polymer side chains. Here, a poly(fluorene‐co‐phenylene) polymer that contains a self‐immolative linker as part of its sidechains is reported. The self‐immolative linker is stabilized with a tert‐butyldimethylsilyl ether group that, upon treatment with tetra‐n‐butylammonium fluoride (TBAF), undergoes a 1,6‐elimination reaction to release the sidechain. Sonication of this polymer with SWNTs in tetrahydrofuran (THF) results in concentrated dispersions that are used to prepare polymer‐SWNT thin films. Treatment with TBAF caused side‐chain cleavage into carbon dioxide and the corresponding diol, which can be easily removed by washing with solvent. This process is characterized by a combination of absorption and Raman spectroscopy, as well as four‐point probe measurements. The conductance of the SWNT thin films increased ≈60‐fold upon simple TBAF treatment, opening new possibilities for producing high‐conductivity SWNT materials for numerous applications. Single‐walled carbon nanotubes (SWNTs) are selectively dispersed with a novel poly(fluorene‐co‐phenylene) having a self‐immolative linker within its sidechains. Cleavage of the linker causes rapid removal of the sidechains, allowing the SWNTs to closely contact one another. Within a thin film, this led to an immediate 60‐fold increase in conductivity, opening new possibilities for producing high‐conductivity SWNT materials for numerous applications.