Co-polymers of aniline and nitroanilines. Part I. Mechanism of aniline oxidation polycondensation

Polyaniline and its co-polymers with o-nitroaniline have been synthesized b y the chemical oxidation of aniline and o-nitroaniline in 0.22M (NH4)(2)S2O 8 + 1M HCl aqueous solution. The yield of product was in the range 51.1-75. 2%. Considering a close similarity between oxidation in chemical and electr ochemical processes, the nature of the intermediates of polyaniline synthes is have been proposed based on cyclic voltammograms. The first stage of the polyaniline synthesis in both electrochemical and chemical oxidation of an iline was found to be the formation of C6H5-NH2+. cation-radical through th e transfer of electron from 2s energy level of nitrogen atom to the electro de during electrochemical oxidation. The electronic structure of the initia l components and intermediate particles of different charge and multiplicit y have been calculated and the most energy suitable structures and the path s of their transformations have been determined. The mechanism of the step- by-step condensation of aniline includes one-electron aniline oxidation int o corresponding cation-radical with subsequent recombination with the prior radical. The recombination proceeds according to the 'head-to-tail' type, which fact is indicated by the minimum value of the total and electronic en ergy equal to -205 402 and -1 204 688 kJ mol(-1), respectively. Nitroanilin es by themselves condense under neither chemical nor electrochemical oxidat ion, although there are no reasons for it regarding their electronic struct ures. (C) 2001 Elsevier Science B.V. All rights reserved.