Effect of protonation media on chemically and electrochemically synthesized polyaniline

Polyaniline films have been prepared both chemically and electrochemically using formic ('Pani-Formic'), boric ('Pani-Boric') or acetic acid ('Pani-Ac etic') as protonation media. Among the three, formic acid seems to be a bet ter protonating medium because it selectively yields the conducting phase o f polyaniline. The variation of potential with the amount of oxidizing agen t suggests one dimensional growth of polymer chain, which proceeds through a PG/EM mechanism as indicated by spectral data. The Pani-Boric and Pani-Ac etic acid demonstrate three- and four-step decomposition patterns, respecti vely, with complete decomposition at about 760 degrees C. Pani-Formic acid, in contrast, reveals a three-step decomposition pattern with 90% weight lo ss at about 900 degrees C and shows a tendency to react with the Pt sample holder. The films of polyaniline generated electrochemically also suggest f ormic acid to be a better protonating medium for achieving a relatively gre ater fraction of conducting emeraldine salt. However, boric acid produces e xcellent quality adherent films with very high deposition rate. Morphologic al features give strong support to this observation. The films of Pani-Form ic and Pani-Acetic acids show a spongy network and globular morphology, res pectively, while Pani-Boric acid yields an extremely uniform surface coatin g. Furthermore, cyclic voltammetry reveals different patterns depending upo n the formation of different oxidation states and the results are in accord ance with optical absorption studies. (C) 2000 Society of Chemical Industry .