Optical absorption and vibrational spectroscopy of conducting polypyrrole under pressure

Polypyrrole in its conducting form was chemically synthesized using p-toluenesulfonic acid as doping agent. UV–Vis absorption and vibrational spectroscopy was used for characterization of the electronic properties. The measurements were conducted under high pressure up to 4 GPa which allows for observation of changes of the structural parameters without changing the chemical nature. The results are interpreted in terms of the stability of charge carriers. A change of the character of the charge carriers from bipolarons to polarons is suggested.