OXIDIZED AND REDUCED POLY(2,5-DI-(-2-THIENYL)-PYRROLE) - SOLUBILITIES, ELECTRODISSOLUTION AND MOLAR-MASS

Oxidized poly(2,5-di-(-2-thienyl)-pyrrole was synthesized electrochemi cally from a 5 to 20 mM monomeric solution in 0.1 M LiClO4 + acetonitr ile (ACN). The electrochemical behaviour of films was studied in 0.1 M LiClO4 aqueous solution, where an insoluble reduced form was found. S olubilities of both oxidized and reduced states were determined in DMS O, acetone and ACN. Their densities and electrical conductivities were also obtained. The solubility of the reduced form is about 15 times h igher in DMSO and ACN than that of the oxidized form. The oxidized pol ymer is insoluble in ACN solutions of perchlorate salts. The high solu bility of the reduced state in this medium allows a quantitative elect rodissolution of the polymer following the reduction process. Results from electrochemical experiments, ultramicrogravimetry and elemental a nalysis indicate an average presence of 0.65 ClO4- ions per monomeric unit incorporated in the oxidized polymer. Both states contain soluble oligomers with from two to six monomeric units, as detected by mass s pectrometry (fast atom bombardment). The molecular mass of these oligo mers indicates a loss of two protons per monomer incorporated in the p olymer, in agreement with an electropolymerization mechanism involving polycondensation of radicals.