Electrocatalytic Oxidation of 2,5-Dimercapto-1,3,4-thiadiazole by Polyaniline. 1 Use of N,N’-Diphenyl-p-phenylenediamine as a Model Compound of Polyaniline

In the present study, electrocatalysis by polyaniline was investigated using a model compound of polyaniline, N,N’-diphenyl-p-phenylenediamine (DPPD). Electrochemical measurements indicated that the highest oxidized form of DPPD, diimine, showed high electrocatalytic activity toward the oxidation of 2,5-dimercapto-1,3,4-thiadiazole, DMcT. On the contrary, one-electron oxidized form of DPPD, radical cation, shows only poor activity in the oxidation. Different electrocatalytic activity observed for polyaniline in the emeraldine salt form and the DPPD radical cation suggests that conductivity of polyaniline in the emeraldine salt form plays an important role in electrocatalysis by polyaniline. Based on the results it was expected that the use of DPPD and its oxidized form as model compounds for polyaniline in the different oxidation states is useful for discussion of relative contributions from redox polymer character and conducting polymer character of polyaniline in electrocatalysis.