The in situ UV-Vis spectra of electropolymerization of m-toluidine and o-toluidine on indium tin oxide (ITO) conducting glass electrode by potentiostatic method in sulfuric acid of 0.5 mol稬^-1 show that the electropolymerization of o-toluidine is faster than that of m-toluidine under the same condition. The current transient curves of electrolyzing m-toluidine and o-toluidine at potential 0.9 V (vs saturated Ag/AgCl) indicate that both poly(m-toluidine) and poly(o-toluidine) are deposited on ITO electrode in three-dimensional progressive nucleation (3DPN) at the beginning of electropolymerization; then the electropolymerization of o-toluidine keeps in branch chain reaction and the electopolymerization of m-toluidine becomes slow greatly. Due to the difference of the electropolymerization of them, the scan electron microscope morphology of poly(o-toluidine) is granulous and porous and that of poly(m-toluidine) is compact and slightly smooth. DFT geometry optimization using B3LYP/6-31G** basis set for the tetramer of o-toluidine and m-toluidine demonstrates that the emeraldine base (EB) for tetramer of m-toluidine has curly structure but EB for tetramer of o-toluidine not, which implies that the conformation difference between poly(m-toluidine) and poly(o-toluidine) might be main cause of the difference of their electropolymerization.

Key words: o-toluidine, m-toluidine, electrocopolymerization, UV-Vis spectrometry