The structure of carbon nanotubes and their electronic interaction with a matrix are important for extracting the unprecedented electronic properties, which have yet to be explored. Here we investigate the dispersibility of single-walled carbon nanotubes (SWNTs) in ionic liquid-derived polymers (PILs), revealed by cross-sectional transmission electron microscopy, infrared optical spectroscopy, and Raman spectroscopy. Surprisingly, SWNTs studied here are highly dispersed, at least down to 7.5 nm-fibres, in a trimethylammonium-suspended PILs. Based on this discovery, we found that the well-dispersed and almost fully dispersed SWNTs in PILs are responsible for the enhanced thermoelectric properties, a future energy harvesting technique.