HIGHLY ORIENTED POLYACETYLENE - STRUCTURES AND ELECTRICAL-CONDUCTIVITY OF THE COMPOUNDS DOPED WITH ALKALI-METALS AND SELECTED OXIDANTS

Films of polyacetylene synthesized according to Akagi method present a high degree of crystallinity. A 6-7 times stretching of these films results in the orientation of the polymer fibers: The mosaic was +/- 5 degrees. Such highly oriented polyacetylene (HOPA) films were chemically doped by heavy alkali metals in the vapor state and electrochemically with GaCl4- anion in nitromethane medium. The evolution of the structures and the variation of the electrical conductivity upon doping were examined in both cases. Doping with alkali metal leads to the appearance of different intercalated phases: The commensurability of these phases is discussed as a function of the nature and the concentration of the intercalated alkaline ion. The electrical maximum room temperature conductivity, which depends on the nature of the alkali metal, is maximum for K-doped materials. In the case of GaCl4- doping, the unique intercalated phase observed is poorly organized except in the chain direction where a GaCl4- ion is found every 4.5 (CH) units. The room temperature electrical conductivity measured along the chain axis is equal to 15 000 S/cm, one order of magnitude higher than the value observed in Shirakawa unoriented polyacetylene.