Electropolymerization of benzene in a two-phase benzene/acid system: Comparative study in strong proton acid and superacid media

Abstract

Anodic polymerization of benzene can be carried out under two-phase conditions, if the electrode is immersed in the interfacial layer between benzene and acids of different strengths such as methanesulphonic, sulphuric, 20% fuming sulphuric, fluorosulphonic and trifluoromethanesulphonic acids. In all these cases the oxidation of benzene occurred in the interfacial layer only and began in the rather low potential region in the vicinity of 1 V (SCE). The characteristics of the film growth and their electrochemical properties change drastically upon transfer from the usual strong acid to fuming sulphuric acid and then to superacids. In the usual acidic media, the film growth and its cyclic voltammetry are characterized by wide ill-defined oxidation—reduction peaks with a half-height width ((Δ E p) 1 2 of about 500–600 mV. On the contrary, in the superacids a metastable state of the film with sharp oxidation—reduction peaks ((Δ E p) 1 2 up to 80 mV), with a great difference between the oxidation and reduction peak potential ( ∼ 400 mV), was formed. IR spectra have shown that a linear chain structure is obtained in all acidic media apart from methanesulphonic acid and in the case of 20% fuming sulphuric acid, the degree of polymerization is high.