Surfactants and amino acids in the control of nanotubular morphology of polypyrrole and their effect on the conductivity

Polypyrrole nanotubes were prepared by the oxidation of pyrrole in aqueous solutions of methyl orange and in the presence of 1–5 wt% of surface-active additives, surfactants, or amino acids. Three types of additives – anionic, non-ionic, and cationic – have been tested in the control of polypyrrole morphology and conductivity. The morphology of nanotubes was little dependent on surfactant type but the changes in size and aspect ratios were more pronounced with amino acids. Except for anionic surfactant, bis(2-ethylhexyl) sulfosuccinate, which behaved indifferently, all additives reduced the conductivity of polypyrrole, some even by four orders of magnitude. Based on FTIR spectroscopy, it is proposed that the hydrophobic interactions and/or hydrogen bonding between the additives and growing polypyrrole chains play the important role in reducing chain ordering, while the ionic interactions have limited effect.