The interactions between poly{(2,6-pyridinyle-nevinylene)-co-[(2,5-dioctyloxy-p-phenylene)vinylen e]} (PPyPV) and SWNTs have been investigated using UV-Vis absorption spectroscopy. The SWNTs promoted polymer organization. PPyPV is a Lewis base and can be doped by strong and weak Lewis acids. The basicity strength of the PPyPV depended on the polymer interchain interactions, which were enhanced by the presence of SWNTs. As the SWNT concentration was increased, an increment in the K-b of PPyPV was observed.