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 320 nm and emeraldine salt phase 740 nm in HCl and HClO₄ while in case of H₂SO₄ media the pernigraniline phase is observed 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. I₁₅₁₀/I₁₄₄₀ 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.