Potentiometric and UV–vis characterisation of N-substituted polyanilines

Poly(N-methylaniline) (PNMeANI), poly(N-ethylaniline) (PNEtANI), poly(N-propylaniline) (PNPrANI) and poly(N-butylaniline) (PNBuANI) films were polymerised on glassy carbon and tin oxide (TO) substrates in 1.0 M HClO4. The pH sensitivity of the polymer films was investigated with potentiometry and UV–vis measurements in aqueous buffer solutions with pH 2–9. The results of these measurements were compared with polyaniline (PANI) prepared in 1.0 M HCl. In this study, the potential and the UV–vis spectrum of the different polymer films deposited on TO were measured simultaneously. These optopotentiometric measurements give information about the surface and bulk processes in the N-substituted polyaniline films when they are in contact with the buffer solutions of different pH. It was shown that the N-substituted polyaniline films were not pH sensitive. The suppressed potentiometric pH sensitivity of the N-substituted polyanilines, which were observed when changing pH, are caused by reduction of the polymer films from their emeraldine to leucoemeraldine oxidation state. Polymerisation of PNMeANI in 0.1 M dodecylbenzenesulphonic acid (DBSA) solution is also reported in this paper.