INVESTIGATIONS OF THE CHEMICAL INTERACTIONS BETWEEN MOLECULAR-OXYGEN AND PRISTINE (UNDOPED) POLYPYRROLE

Polypyrrole is unique among the heterocyclic conductive polymers in that the undoped (i.e., pristine) form of the polymer is oxidized by molecular oxygen. Because of the O-2 reactivity of pristine polypyrrole, it has been difficult to prepare and characterize the pristine material. We have recently solved this problem through the use of a rigorously airtight infrared spectroelectrochemical cell. This new spectroelectrochemical cell has provided an opportunity to explore the fundamental chemistry of the interaction between molecular oxygen and pristine polypyrrole. We have found that pristine polypyrrole interacts with O-2 via three primary pathways. The first entails partial electron transfer to O-2 to form a molecular association complex. Such complexes have been observed for monomeric pyrroles. The second process is analogous to oxidative doping and involves complete electron transfer to form the polycationic version of the polymer with the superoxide anion as the counterion. Finally, after long times (i.e., hours) the superoxide anion deprotonates the polymer to yield an imine form of polypyrrole.