The model for optical properties of PPP-type polymers.

The recently successful model [1, 2] for optical properties of PPV based po lymers is applied to the PPP family. More progress is available thanks to a nalytical results covering not only spectra but also the oscillator strengt h. We conclude similar assignments and emphasize the delocalized nature of basic features. We demonstrate the existence of different types of Coulomb excitons and their roles in the optical absorption. An important and intrig uing difference compared with PPV based polymers is the level inversion for the more strongly localized interband exciton. Comparison is made to avail able optical and EELS data [3, 4, 5]. Our conclusions are suggestive for th e future light polarized experiments.