Electrochemical aspects of polypyrrole

The expulsion of H + during electrochemical polymerization of pyrrole in aqueous solution has been found by titration to be close to 2H + (over 70?0)per pyrrole monomer polymerized. The first reduction scan of polypyrrole as polymerized, PPy~+(yX-), during cyclic voltametry run in CH3CN solution containing the supportin~ electrolyte Et4N+X- from 0 to -0.8 V vs SCE showed a well defined de-intercalation peak with very small residual currents. From the charge consumed in the de-intercalation peak q2 and the charge consumed in polymerization ql one can find the value of 9 by 9- 2q2/(ql-q2). From in-situ observation of the VIS spectrum of electrochemically reduced PPy the inter-band absorption peak wavelength offers an estimation of the conjugation length of PPy prepared, which is usually rather short being 4-5. The possibility of spontaneous anion exchange between X- in PPy(X-)and Y- in aqueous solution has been studied. Examples of fast and complete exct~ange as well as those of partial, difficult and no exchange are given. Quasi-equilibrium electrode potential for Pt,PPy(CI-)ICI- has been studied and a Nernst electrode response to Cl- concentration in solution was found.