The present invention relates to a one-step process for preparation of “in-situ” or “ex-situ” self-organized and electrically conducting polymer nanocomposites using thermally initiated polymerization of a halogenated 3,4-ethylenedioxythiophene monomer or its derivatives. This approach does not require additional polymerization initiators or catalysts, produce gaseous products that are naturally removed without affecting the polymer matrix, and do not leave by-product contaminants. It is demonstrated that self-polymerization of halogenated 3,4-ethylenedioxythiophene monomer is not affected by the presence of a solid-state phase in the form of nanoparticles and results in formation of 3,4-polyethylenedioxythiophene (PEDOT) nanocomposites.