Poly(methyltetraphenylphenylsilylene-co-bis(methylphenylsilyl)acetylene) (PSA) was synthesized by the cocondensation reaction of methyltetraphenylphenyldichlorosilane and bis(chloromethylphenylsilyl)acetylene with sodium in toluene. The PSA thus obtained was soluble in most organic solvents

and its molecular weight was smaller than that of poly[(disilanylene)acetylenes] with alkyl- or aryl-substitution because of the great steric congestion of tetraphenylphenyl groups. The optical and electronic properties of the polymer were investigated. The results show that PSA has strong UV absorption and fluorescence emission

the maximum UV absorption wavelength of PSA is 330 nm

which shows a considerable red-shift in comparison with that of poly(methylphenylsilylene-co-methylphenylsilylacetylene) (PSI) and alkyl- substituted poly[(disilanylene)acetylenes]. A strong photoluminescence band at 470 nm in THF and 432 nm in benzene can be observed in the visible region

respectively. Treatment of the films of PSA with I2 vapor afforded conducting films. The conductivity of PSA thin film doped with I2 was measured to be 0.35 S cm-1 in the air which is lower than that of poly(methyltetraphenylphenylsilylene-co-bis(methylphenylsilyl)phenylene)

but higher than that of σ-π polymers without tetraphenylphenyl groups. As an explanation

the tetraphenylphenyl group is a large π-electron-conjugated group; after being introduced to the Si atoms of the polysilanes

the interaction between π-electrons of the tetraphenylphenyl groups and the σ-electrons conjugated along the Si—Si bonds is increased strongly

and the σ-electrons can be conjugated more extensively along the main chain of the polysilanes.