Acid Blue dyes in polypyrrole synthesis: The control of polymer morphology at nanoscale in the promotion of high conductivity and the reduction of cytotoxicity

Polypyrrole has been prepared by facile single-step chemical oxidative polymerization of the monomer in aqueous medium containing an anthraquinone dye, Acid Blue 25 or Acid Blue 129. The addition of the former structure-guiding agent results in the formation of polypyrrole nanowires with conductivity improved up from the units S cm^–1 to 60 S cm⁻¹. The second closely related dye, Acid Blue 129, had no impact on polymer morphology but in its presence the conductivity of polypyrrole also increased. It has been shown that the pyrrole concentration and oxidant-to-pyrrole mole ratio significantly affect the conductivity of synthesized polypyrrole. Polypyrroles have been characterized by FTIR and Raman spectroscopies to assess their molecular structure and intermolecular interactions. Considering the applications in biomedicine, the cytotoxicity of the samples has also been tested. Polypyrrole prepared with Acid Blue 129 has significantly lower cytotoxicity compared to that prepared with Acid Blue 25. The cytotoxicity of both polypyrroles can be eliminated by purification step. Low cytotoxicity combined with high conductivity enables application of these conducting polymers in biomedicine.