Synthesis and Characterization of Polyaniline Nanotubes by Template-free Method

A practical way to synthesize polyaniline nanotubes was developed using ammonium persulfate (APS) as the oxidant in the absence of any templates and acidic dopants. The structure, morphology and property of the product were characterized by FTIR spectrometry, UV-Vis spectrophotometry, transmission electron microscopy and X-ray diffraction. Polyaniline nanotubes with the outer diameter of ca. 80 nm, inner diameter of ca. 10 nm and the length of 26 mu m were obtained with the aid of ultrasonic irradiation. Due to the protons produced during the polymerization, the pH value of the solution decreased with the increasing polymerization time and the polymerization rate increased with the aniline concentration. However, the morphology of polyaniline was irrelevant to the aniline concentration, but affected by the molar ratio of aniline to APS. Ultrasonic irradiation played an important role in the formation of polyaniline nanotubes. It prevented the rapid agglomeration of spherical micelles and made the self-assembly of micelles more orderly. As a result, polyaniline nanotubes can be synthesized at a higher aniline concentration. The conductivity of polyaniline was determined to be 5 x 10(-3) S.cm(-1).