The transport properties of metallic shirakawa polyacetylenes with different dopant species

Summary form only given. A series of investigations were made on metallic Shirakawa polyacetylenes (S-PA) (/spl sigma/ =200-30OS/cm) doped with various kinds of halogens and protonic acids. We aim to clarify the influence of different dopant species on the electrical transport properties. Extensive measurements between 1.6-300 K were made of the Voltage-Shorted-Compaction (VSC) resistivity (pvsc), the absolute thermoelectric power S(T) and the ordinary 4-terminal resistivity. S(T) assumed small positive values at 300K of 7/spl mu/V/K for both HCl0/sub 4/ and ClSOH/sub 4/ doped PA, and 15/spl mu/V/K for I/sub 2/ doped PA. The temperature dependence also exhibited the typical metallic character as a whole but showed clearly different manners for PA´s with different chemical species as dopant. S(T) was almost proportional with temperature over the en,.ire temperature range in HCl0/sub 4/ and ClSO/sub 3/H doped PA. In I/sub 2/ doped PA, on the other hand, the temperature dependence of S(T) can be divided into two regimes. S(T) is linear for temperatures above 100K, the extrapolated value at T=O being +3/spl mu/VV/K, while S(T) decreases towards zero with a curvature below IOOK. The difference indicates that the transport properties of carriers along the polymeric chain are affected differently by the dopant species with different chemical structure. We will also show that the behaviour of pvsc is similar to that of S(T), lending support to the above idea.