Optical absorption and vibrational spectroscopy of conducting polypyrrole under pressure

Polypyrrole in its conducting form was chemically synthesized using p-tolue nesulfonic acid as doping agent. UV-Vis absorption and vibrational spectros copy was used for characterization of the electronic properties. The measur ements were conducted under high pressure up to 4 GPa which allows for obse rvation of changes of the structural parameters without changing the chemic al 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. (C) 2001 Elsevier Science B.V. All rights reserve d.