The conjugated polymer poly(2,5-dihexyl-1,4-phenylene-alt-2-amino-4,6-pyrimidine) was synthesized and used in the supramolecular functionalization of single-walled carbon nanotubes (SWNTs). It was found that this polymer can form strong supramolecular polymer–nanotube assembly and produce a stable composite in solution. The resulting polymerized nanotubes were analyzed by UV–Vis absorption and emission spectroscopy, thermogravimetry, transmission electron microscopy and scanning electron microscopy. It was found that the noncovalent functionalization did not damage the nanotube structure. The polymer content in the polymer–nanotube composite could be calculated to be 41% by thermogravimetry analysis. The composite exhibited certain solubility in dimethylacetamide (DMAc), where the solubility in the absence of excess free polymer solution is 78.7 mg L−1. The composite exhibited a conductivity of 0.005 S cm−1 and the anodic and cathodic peaks were observed at 0.47 and 0.37 V. Galvanostatical charge/discharge tests give good cycling behavior of maintaining a stable capacitance value of 66.7 F g−1 over 1000 cycles at a current load of 1 mA cm−2 without distinct drop.