The interaction of N-methyl-2-pyrrolidone (NMP) and organic acid doped
polyaniline (PAn) is studied by UV-Vis-NIR spectroscopy. A dedoping e
ffect is observed when the doped PAn solution is extremely diluted by
NMP. This effect is due to a strong interaction between NMP and the do
pant acid. The competition between NMP and PAn is responsible for the
poor conformation of doped polyaniline in NMP solution and the poor co
nductivity of the film cast from this solution.