Electronic Properties of Conjugated Polymers with Aromatic or Hetero-Aromatic Cycle

Abstract

In this paper, we present an investigation of the vibrational properties of a series of conjugated polymers containing aromatic or heteroaromatic rings. By Resonance Raman Scattering (RRS) and IR absorption, we measure the frequencies of the vibrational modes which are then analyzed in the frame of a valence force field model. In our calculations, we have included the results obtained in a number of oligomers or model compounds. A good determination of the main force constants, associated with carbon-carbon bonds, is made by fitting experimental data. In undoped polymers (PPP, PPV, PTV and PFV), these parameters are in good consistency with an aromatic structure along the polymeric chains. In p-doped PPP and p-doped PPV, Raman spectra which are observed experimentally are modified with a shift of some Raman bands. These modifications are well interpreted by a change in the force constants in good agreement with a quinoid-like structure.