Conducting Polymers: IR and Raman Studies

Abstract

As part of a study into the the electronic conductivity of conducting polymers and their use in gas sensors, the infrared reflectivity of polypyrrole and polyaniline and the Raman spectra of polypyrrole were measured and examined. Infrared reflectivity spectra presented are: comparisons of PF6-doped polypyrrole at different synthesis temperatures, comparisons of polypyrrole doped with PF6 and dodecylbenzenesulphonate (DDBS), room temperature and 10 K measurements on PF6-doped polypyrrole, PF6-doped polypyrrole in a moisture rich atmosphere, the effect of 'dedoping' of PF6-doped polypyrrole and polyaniline samples blended with various copolymers. Optical conductivity and dielectric constant spectra accompany the reflectivity spectra. In generating these optical constants great care was taken that they should be Kramers-Kronig consistent by using a fitting function to generate the low frequency extrapolation rather than assuming applicability of the Hagen-Rubens relation. Raman spectra are presented for polypyrrole doped with PF6, paratoluenesulphonate and DDBS. Investigations into conducting polymers observe a mixture of metal-like and non-metal-like properties. A suggested heterogeneous model represents the material as a compound of metallic and non-metallic components. By applying an extension to this model for AC conductivity, it is shown that the infrared reflectivity supports the heterogeneous interpretation.