Raman study of trans-polyacetylenes doped with electron donor and acceptors

The Raman spectra of trans-polyacetylene films doped heavily with electron donor (Na) and acceptors (iodine, SO₃, HClO₄ FeCl₃) were studied with excitation wavelengths between 488.0 and 1320 nm. The observed Raman bands are attributed to negatively and positively charged domains created by donor- and acceptor-doping, respectively. The observed large wavenumber dispersion of the C=C stretching vibration (v₁ band) of charged domains suggests a broad distribution of localization lengths in the charged domains. The charged domains generated by doping are localized over not more than eleven conjugated C=C bonds. The observed wavenumber of the v₂ band (CC stretch) of the acceptor-doped forms is higher than that of the corresponding band of pristine trans-poylacetylene, whereas the contrary is the case for the donor-doped forms.