Conductivities of polysilanes

Measurements of the electrical conductivities of three types of polysilanes were carried out over a range of dc fields and temperatures. These polymers are varied in substituents and structures with formulas of C₆H₅SiCH₃]_n, (C₆H₅SiCH₃)₇₀(CH₃SiH)₃₀]_n, and (C₆H₅SiCH₃)₅₀(C₆H₅SiH)₃₀(CH₃Si)₂₀]_n. Undoped polysilanes behaved as insulators since their conductivities were observed in the range of 10^?10 to 10^?13 S cm^?1, while SbF₅-doped polysilanes of all kinds behaved as semiconductors with conductivities in the range of 10^?2 to 10^?4 S cm^?1. No significant difference in conductivities was observed among three SbF₅-doped polysilanes although these polymers are very different in chemical properties. These experimental results suggest that electrical conductivities of polysilanes are associated with the Si? Si main-chain backbone rather than with the side groups. It is evident that the dopant is able to diffuse throughout the bulk of the polymer and the conductivity of the doped polymer is a function of the dopant concentration from the result of in situ monitoring of the resistance of the silane homopolymer during SbF₅ doping at room temperature. The conductivities of polysilanes appeared to be temperature-dependent. The activation energy for the conduction of SbF₅-doped silane copolymer was found to change at its glass transition temperature. © 1996 John Wiley & Sons, Inc.