Spectroscopic studies of doping reactions in polypyrrole actuators

Thin films of polypyrrole were electropolymerised on a platinum electrode in electrolytes containing the small mobile chloride anion, the doubly charged sulfate anion and the bulky dodecyl benzene sulfonate (DBS) anion, and tested by in situ Raman spectroscopy using laser excitations of 488 nm and 785 nm. Cyclic voltammetry indicated that anion movement dominates the redox processes in a KCl electrolyte, and cation movement in NaDBS media, while in K2SO4 both anions and cations are involved during doping and dedoping. The reduction of polpyrrole was effectively monitored by the increase of the 1555 cm−1 band (νCC) using the 488 nm laser, and the oxidation of polpyrrole by the appearance of a band at 921 cm−1 (δCH) using the 785 nm laser.