New σ-π conjugated alternating silylene-diacetylene copolymers, –[(SiMe2)m–C≡C–C≡C]n–, m = 1, 3, 4, and 6, were synthesized by the reaction of α,ω-dichloropermethylated oligosilanes with dilithiobutadiyne, LiC≡C–C≡CLi. The IR spectra clearly indicated the presence of diyne unit in the polymer backbone. The influence of the chain length m of the dimethylsilylene unit in the –[(SiMe2)m–C≡C–C≡C]n– backbone on the optical and the electrical properties was investigated.