Polypyrrole

A Polypyrrole (PPy) is a chemical compound formed from a number of connected pyrrole ring structures. For example a tetrapyrrole is a compound with four pyrrole rings connected. Polypyrroles are conducting polymers of the rigid-rod polymer host family, all basically derivatives of polyacetylene. Polypyrrole was the first of this key family of compounds to show high conductivity.

In a series of papers in 1963, DE Weiss and coworkers reported  high-conductivity (up to 1 S/cm) in iodine-doped oxidized polypyrrole. While too early and thus eventually "lost", this anticipated by many years the Nobel-prize-winning discovery of high-conductivity in similarly iodine-doped and oxidized polyacetylene, as well as John McGinness' et als report of a high-conductivity "ON" state in the putative first organic electronic device.

Polypyrroles are also called pyrrole blacks or polypyrrole blacks. Polypyrroles also exist naturally, especially as part of a mixed copolymer with polyacetylene and polyaniline in some melanins.

In 2006, scientists from Brown University published work on a fast-charging and discharging battery chemistry based on polypyrroles.