Chemical reduction of the emeraldine base of polyaniline by reducing agents and its kinetic study

Abstract

Abstract The reduction of the emeraldine base form of polyaniline (PEM) by N , N ‐diethylhydroxylamine, sodium tetrahydroborate, sodium dithionite, and hydrazine 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 ), N , N ‐diethylhydroxylamine (6,2 · 10 −2 mol · L −1 ), and NaBH 4 (1,13 · 10 −3 mol · L −1 ) are 1,46 · 10 −4 S −1 , and 2,50 · 10 −4 s −1 , and 1,7 · 10 −3 s −1 at 20°C, respectively. In the case of sodium dithionite, which has a higher reducing ability, the reduction proceeds very rapidly at room temperature. Plot of In( k /[reductant]) against the electrochemically measured half‐wave potential E 1/2 affords a linear correlation with a slope of 20 V −1 .