Role of H+ in Polypyrrole and Poly(3,4-ethylenedioxythiophene) Formation Using FeCl3·6H2O in the Room Temperature Ionic Liquid, C4mpyrTFSI

Abstract

The polymerisation reaction of pyrrole and 3,4-ethylenedioxythiophene using the chemical oxidant FeCl3·6H2O in the room temperature ionic liquid butyl-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (C4mpyrTFSI) has been investigated using cyclic voltammetry, UV/vis and IR spectroscopy. The voltammetric data for the Fe2+/3+ reaction is complicated by the presence of H+ introduced upon dissolution of the iron salt by deprotonation of the coordinated waters. The voltammetric and chemical reaction studies show that H+ itself, introduced to solution as trifluoromethanesulfonic acid (HTFSI), can act as the chemical oxidant for the polymerisation reaction. Voltammetric data also implies that in this system the Fe2+/3+ redox couple may not actually be involved in the polymerisation reaction and that the H+ introduced upon dissolution of the FeCl3·6H2O may be the sole cause of the oxidation reaction.