MOSSBAUER-SPECTROSCOPY OF HIGHLY-ORIENTED POLYACETYLENE DOPED WITH I-129

The Mossbauer spectroscopy has been applied to high density polyacetyl ene films doped with I-129. In addition to the well-known polyiodide a nions, I3- and I5-, a new iodine species Ialpha has been found in the present study. The new species Ialpha has been assigned to the iodine atom covalently bound to the chain carbon. Although the iodine Ialpha introduces sp3-carbon defects interrupting the alternation of single a nd double bonds of the chain, the amount of Ialpha has been estimated to be lower than a critical sp3-carbon concentration which is a theore tically predicted value to break the highly conductive phase of iodine -doped polyacetylene. From the angular dependent Mossbauer spectra obt ained under the condition that the oriented direction of the polymer i s parallel and perpendicular to the propagating direction of the incid ent gamma-rays, it has been revealed that the molecular axes of I3- an d I5- are aligned along the oriented direction of the polymer.