Conducting polymers are studied because of their conductivity, as functional materials, and for their ability to respond to external stimuli. Polyaniline, polypyrrole, and poly(3,4-ethylenedioxythiphene) are typical conducting polymers. They are investigated alone, or as components of composite materials. Their structural characterization, their physical and chemical properties, and their applications, in both well-established and new surprising directions, are of interest.
In the Department of Conducting Polymers, oxidative chemical polymerization is the main synthetic tool. Conducting polymers are prepared as powders, which can have granular or nanotubular morphology. Thin polymer films are deposited on virtually any surface immersed in the reaction mixture. Colloidal dispersions are obtained if a water-soluble polymer stabilizer is present. Hybrid composite particles are produced by the coating of various inorganic materials with conducting polymers. Carbon nanotubes, montmorillonite, silica, or ferrites can serve as examples of the inorganic component.
The morphology-retaining carbonization of conducting polymers, composites of conducting polymers with noble metals, viz. silver, and the combination of conducting polymers with ionic liquids belong among recent interests of the department. The traditional methods of polymer synthesis, however, are also developed.
The department has focused on the preparation and characterization of conducting polymers in general, and polyaniline in particular. The produced materials are currently tested in cooperating institutions as semiconductors, analytical electrodes, sensors, flame retardants, catalyst supports in heterogeneous catalysis, in the corrosion protection of metals, in fuel cells, electrorheology, gas separation, and in other applications.
Preparation of Polyaniline
The oxidation of aniline with ammonium peroxydisulfate in acidic aqueous medium yields protonated PANI salt. Sulfuric acid and ammonium sulfate are by-products.
After deprotonation by ammonium hydroxide, the conducting protonated PANI gives the non-conducting PANI base and the ammonium salt of the protonating acid.
Polyaniline exists in several forms that easily transform in acid/base and redox transitions. The electrical, optical, and chemical properties change correspondingly.
J Stejskal, P Kratochvíl, A D Jenkins, Polymer 37, 367 (1996)