Synthesis of free-standing poly(3,4-ethylenedioxythiophene) conducting polymer films on a pilot scale

Electrochemical polymerization of 3,4-ethylenedioxythiophene (EDT) was carried out in the presence of monomeric anions or polyanions in electrolyte solutions. While no free-standing films of poly (3,4-ethylenedioxythiophene) (PEDT) were obtained using monomeric anions as dopants, flexible conducting polymers were obtained using novel polyanions, e.g., sulfated poly(β-hydroxyethers) (S-PHE), sulfated poly(β-hydroxyethers) having trifluoromethyl groups (S-PHEF), and sulfated polybutadiene (S-PBD). The conductivity of these PEDT/ polyanion composites exceeded 150 S/cm, and reached as high as 400 S/cm when S-PHEF was used as dopant. These conducting composites demonstrated superior mechanical properties, and PEDT/S-PBD showed an elongation of 78–110% at 100 °C. The electrical properties were strongly dependent on the synthesis conditions. The important parameters were optimized for the S-PHE polyanion. By doing this the conductivity of the PEDT/S-PHE composite reached values around 230 S/cm. Based on the optimized parameters, a continuous synthesis of PEDT/S-PHE composite was developed leading to reproducible conducting composites. The electrode is cylindrical and 10 cm wide. The computer-controlled system enabled the preparation of PEDT films more than 20 m long.