SOME CHEMICAL AND ELECTRONIC-STRUCTURES OF THE NONCONJUGATED POLYMER POLY(3,3'-PHTHALIDYLIDENE-4,4'-BIPHENYLENE)

The valence band structure of poly(3,3'-phthalidylidene-4,4'-biphenyle ) has been studied using ultraviolet photoelectron spectroscopy (UPS). This polymer exhibits a dielectric-to-metal phase transition under th e influence of external forces and is therefore a good candidate for s tudying charge instabilities in conjugated polymers. Interpretation of the UPS spectra is facilitated using quantum chemical calculations ba sed on the semi-empirical Austin Model 1 (AM1) method, for geometry op timization, and the valence effective Hamiltonian (VEH) method, for ca lculating the energy band structure diagram, from which the density of valence states (DOVS) in the solid material is derived. The calculate d DOVs is in good agreement with the experimental UPS spectra, enablin g an identification of features in the experimental data in terms of s pecific features in the energy band structure.