Properties of nanometric and micrometric multilayered films made of three conducting polymers

The electrochemical, electrical and morphological properties of multilayered films formed by alternated layers of poly(3,4-ethylenedioxythiophene), polypyrrole, and polyN-(2-cyanoethyl)pyrrole], which were prepared by electrochemical layer-by-layer deposition, have been investigated and compared with those of multilayered films formed by two conducting polymers. Results indicate that the electrochemical behavior of the films formed by three conducting polymers depends on the micrometric or nanometric thickness of the layers. Thus, the electroactivity increases until the thickness of these films reaches a threshold value (∼2 μm), while the electrostability of the films is very remarkable when their thickness is close to ∼4 μm or higher. On the other hand, comparison between multilayered systems made of two and three conducting polymers indicates that the third component introduces heterogeneity in the interfaces between consecutive layers, reducing the ability to store charge. Among the latter, multilayered films formed by poly(3,4-ethylenedioxythiophene) and polypyrrole have been found to be particularly electroactive and electrostable. The surface morphology and topography of the layers have been used to rationalize the electrochemical properties of the different materials.