Self-Forming Microtubes of Polypyrrole: Reaction Conditions and Physical Properties

Polypyrrole microtubes have myriad promising technological applications. The known synthetic routes for preparing the microtubes involve a shape-guiding template which needs to be removed at final stage of the synthesis. We have recently discovered a new synthetic method, by which polypyrrole microtubes spontaneously form during the electropolymerization of pyrrole without any shape-guiding template. Here the reaction conditions for self-formation of polypyrrole microtubes were examined and the favorable conditions to repeatedly synthesize the microtubes were determined. The reaction processes were also traced by a microscope with a CCD camera. The microtubes were found to grow near the free end of microtubes. In addition a small bubble of hydrogen gas, which was attached at the free end of microtube, was suggested to have an important role in the growth of microtubes. The temperature dependence of electrical resistance suggests that the conduction mechanism of microtubes is similar to that of the conventional polypyrrole films.