Synthesis of a polypyrrole film on a non-conducting substrate; the influence of the oxidant and acid concentration

Thin films of conducting polypyrrole are deposited on a non-conducting subs trate by dipping the substrate in a pyrrole solution and subsequently in an oxidising solution containing Fe(ClO4)(3) and HClO4. In this last step pyr role is polymerised by Fe3+. Calculations on the influence of the acid conc entration on the Fe3+ hydrolysis equilibria are in good agreement with UV/V IS and pH measurements. These calculations and experiments in which HClO4 i s replaced by LiClO4, show that the polymerisation rate of pyrrole is deter mined by the perchlorate concentration and not by the acid concentration. W e conclude that the perchlorate ions promote the dimerisation of the radica l cations by reducing the electrical repulsion between the radical cations; therefore the dimerisation of the radical cations is the rate-determining step. (C) 1999 Elsevier Science S.A. All rights reserved.