The intrinsic redox states and protonation behavior of poly( o-toluidine)

Abstract

The intrinsic redox states and protonation behavior of poly( o-toluidine) (POT) are compared with those of polyaniline and 2-chloroaniline polymer, using X-ray photoelectron spectroscopy (XPS) as a primary tool. The POT base can assume a 50% intrinsically oxidized state, or a 50% protonated state, as in the case of emeraldine (EM) base. The methyl-group substituent in POT, however, reduces halogen addition significantly during protonation by HCl of high concentrations. It also hinders the charge transfer interactions of the polymer with bulky organic acceptors, such as o-bromanil. No demethylation is observed during reprotonation or sulfonation of POT base, in contrast with a substantial degree of dehalogenation observed in the 2-chloroaniline polymer during similar treatment. Sulfonation of POT gives rise to a 50% self-protonated polymer, as in the case of sulfonated EM base, but is accompanied by further chain distortion. Further treatment of sulfonated POT with HClO 4 can result in the co-existence of self-doping and external protonation of POT and a protonation level substantially above 50%.