The structure and properties of soluble polyacetylene (PA) obtained with rare-earth catalyst are thoroughly investigated by UV

IR

Raman spectroscopes

ESR and X-ray diffraction. The soluble PA is different with film and powder PA in their spectra and ESR

which arises from the fact that the average molecular weight of the former is much lower than that of the latter. The experimental results indicate that linear PA usually has a critical average molecular weight for solution

and the soluble PA show some specular properties because its average mole-cular weight is below the critical value.