Synthesis and formation mechanism study of rectangular-sectioned polypyrrole micro/nanotubules

Aligned polypyrrole (PPy) micro/nanotubules were synthesized via a self-assembly method using FeCl3 as oxidant and Acid Red 1 (C.I. 18050, 5-(acetylamino)-4-hydroxy-3-(phenylazo)-2,7-naphthalenedisulfonic acid) as dopant. PPy has a typical length of 530 μm and a unique rectangular-sectioned morphology. Its general morphology could be manipulated by varying synthetic conditions including polymerization time, monomer concentration, oxidant species, and stirring. The synthesized PPy and reaction intermediates were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray powder diffraction (XRD), and solubility tests in methanol and water. Our observation and results suggest a plausible formation mechanism of rectangular-sectioned PPy micro/nanotubules. AR1-Fe(II) complex formed from the complexation of Acid Red 1 and Fe2+(reduced from Fe3+), which precipitated in the aqueous solution, might have functioned as 'template' during the polymerization of pyrrole monomers. The conductivity of PPy with different morphologies was also measured and compared.