A soluble pi-conjugated polymer cis-PmPV is found to be twice as effective as its trans-PmPV isomer in dispersing SWNTs into organic solvents. The improved efficiency is related to the specific conformation of cis-vinylene-enriched PmPV, which facilitates a planar pi-pi interaction with SWNT surface and leads to improved nanotube dispersion. H-1 NMR spectra indicate that the cis-CH=CH bonds are partially converted to the trans-CH=CH, thereby providing necessary conformational cavity for SWNT wrapping. Irradiation triggers a precipitation from SWNT dispersion, providing a purified SWNT/conjugated polymer composite. (C) 2009 Elsevier Ltd. All rights reserved.