Synthesis of polypyrrole and polythiophene in aqueous solution of Keggin-type structure heteropolyanions

Immobilization of Keggin-type heteropolyanions (HPA) such as: PMo₁₂O₄₀ ^3-, SiW₁₂O₄₀ ^4-, and PW₁₂O₄₀ ^3- in polypyrrole, poly(3-methyl-thiophene), and polyaniline is performed by electropolymerization of pyrrole (Py), 3-methyl-thiophene (3-MeTh), and aniline (An) in aqueous and nonaqueous solutions in the presence of corresponding heteropolyacids and salts. It was found possible to obtain electroactive films of polypyrrole and polythiophene from aqueous solutions of HPA due to formation of respective HPA-Py and HPA-3-MeTh complexes. Application of acidic environment to the Py polymerization leads to its rapid trimerization and deterioration of electroactive properties of the film obtained. These electrodes were characterized by cyclic voltammetry which provides two one-electron reversible HPA redox systems. They are stable in acidic solutions for poly(3-methylthiophene) and in acidic and neutral solutions for polyaniline.