Microtubules of polypyrrole synthesized by an electrochemical template­free method

Abstract

Microtubules of polypyrrole (PPy) were synthesized by an electrochemical template-free method in the presence of β-naphthalenesulfonic acid (β-NSA) as a dopant for the first time. The influence of electrochemical polymerization conditions, such as material of the working electrode, the concentration of β-NSA and pyrrole monomer, current density and polymerization time on the tubular morphology of PPy-NSA was systematically investigated. PPy-NSA tubules 0.8–2.0 µm in diameter and 15.0–30.0 µm in length were obtained when a non-corrosive steel plate was used as the working electrode, and the size of the tubules was affected by other polymerization conditions. The molecular structure of the tubules was characterized by FTIR and X-ray diffraction, indicating that their polymer chains are similar to granular PPy synthesized by other chemical or electrochemical methods, and the tubules were amorphous. The conductivity of the tubules at room temperature was found to be about 5.0 S cm⁻¹ and the temperature dependence of the conductivity followed a two-dimensional Variable Range Hopping (2D-VRH) model. It was proposed that the absorbed micelles of β-NSA, which result from the surfactant characteristics of β-NSA dopant on the working electrode, act like templates in forming PPy-NSA tubules by this new method.