CHEMICAL-REDUCTION OF THE EMERALDINE BASE OF POLYANILINE BY REDUCING AGENTS AND ITS KINETIC-STUDY

The reduction of the emeraldine base form of polyaniline (PEM) by NN-d iethylhydroxylamine, sodium tetrahydroborate, sodium dithionite, and h ydrazine monohydrate proceeds smoothly at room temperature to give the leucoemeraldine base form of polyaniline (PLM). The reduction of PEM to PLM with these reducing agents obeys a pseudo-first-order kinetics with respect to the concentration of PEM. The pseudo-first-order rate constants, k, of the reduction with hydrazine monohydrate (5,0 . 10(-1 ) mol . L-1), NN-diethylhydroxylamine (6,2 . 10(-2) mol . L-1), and Na BH4 (1,13 . 10(-3) Mol . L-1) are 1,46. 10(-4) s-1, 2,50 . 10(-4) s-1, and 1,7 . 10(-3) s-1 at 20-degrees-C, respectively. In the case of so dium dithionite, which has a higher reducing ability, the reduction pr oceeds very rapidly at room temperature. Plot of ln(k/[reductant]) aga inst the electrochemically measured half-wave potential E1/2 affords a linear correlation with a slope of 20 V-1.