Spectroscopic and electrochemical properties of poly(2,5 dimethyl aniline) films

UV-visible, IR and redox characteristics of electrochemically deposited poly(2,5 dimethyl aniline) films are affected by varying the monomer concentration (0.025, 0.05 and 0.1 M) and dopant anions in the electrolyte solution (HCl, HClO4 and H2SO4) The optical spectra show the presence of reduced leucoemeraldine phase similar to 320 nm and emeraldine salt phase similar to 740 nm in HCl and HClO4 while in case of H2SO4 media the pernigraniline phase is observed similar to 540 nm. The magnitude of absorbance is highest in H2SO4>HCl>HClO4. On the other hand, the selectivity in the formation of conducting phase is greater in HCl in comparison with HClO4 and H2SO4. IR spectra of the film reveal a higher ratio for the relative intensities of the quinoid to benzenoid ring modes i.e. I-similar to 1510/I-similar to 1440 in case of films deposited in H2SO4. Cyclic voltammograms show the presence of a single redox couple in each case except for H2SO4 where an additional anodic peak is observed. However, the increase in current is highest in HCl>HClO4>H2SO4 hence, the thickness of the films calculated for the cathodic peak are in accordance with the current. (C) 1999 Elsevier Science S.A. All rights reserved.