OPTICAL STUDIES ON FREESTANDING POLYPYRROLE FILMS BY THE PHOTOPYROELECTRIC METHOD

Optical spectra of free-standing polypyrrole films were investigated b y a novel PhotoPyroElectric (PPE) method. The reflection and absorptio n spectra in the range 2000-25000 cm(-1) of TsO(-)- and ClO4--doped po lypyrrole films were obtained with an experimental setup comprising tw o pyroelectric sensors. The absorption bands due to electronic transit ions to the bonding and antibonding bipolaronic levels appear at 11 00 0 and 21 500 cm(-1), respectively. Some relevant details in the polypy rrole spectrum in the 2000-5000 cm(-1) range were observed. The absorp tion band located at 3400 cm(-1) is characteristic for NH stretching v ibration. The bands in the 2300-2500 cm(-1) range are ascribed to the vibration of N+H groups containing positively charged nitrogen. The PP E spectra also reveal changes of the electronic and vibrational absorp tion bands after polymer reduction and HCl treatment.