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When ca. 85% cis films of the semiconducting polymer, polyacetylene, (CH)x, are first doped with bromine and then partly dehydrobrominated at 150°C, substitution of II by Br occurs to yield new semiconducting polymers of general composition [CH1-uBry]x, where y=0.003-0.23. These films have been studied using electron paramagnetic resonance (EPR), dynamic nuclear polarization (DNP), and Raman spectroscopic techniques. EPR results indicate that with an increase in bromine substitution, the linewidth (ΔHpp), g-value, and homogeneity of the samples increase. This is consistent with DNP results which suggest a decrease in the diffusion coefficient of unpaired spins as the bromine substitution level increases. Raman results are consistent with bromine substitution and indicate that essentially no change in conjugation length occurs when H is substituted by Br.

A study of Raman scattering from partially isomerized polyacetylene films with varying cis-trans content is presented. Major differences are discovered in the dispersion of trans-(CH)x Raman bands between pure trans- and cis-rich samples. It is shown that the unusual dispersion of the trans-(CH)x Raman bands in partially isomerized samples cannot arise from a distribution of short chains. These results are discussed in terms of the complex response of the lattice to the presence of photoinjected electron-hole pairs.