Synthesis of oligo(dimethylsiloxane)–oligothiophene alternate polymers from α,ω-dibromooligo(dimethylsiloxane)

Treatment of dilithiooligothiophene with α,ω-dibromooligo(dimethylsiloxane) prepared by the Pd-catalyzed dehydrobromination of α,ω-dihydrooligo(dimethylsiloxane) with isopropyl bromide gave polymers composed of alternately arranged oligo(dimethylsiloxane) and oligothiophene units, [(Me2SiO)xSiMe2(C5H2S)y]n (x = ca. 8, y = 2–5). A similar reaction of α,ω-dibromooligo(dimethylsiloxane) with 5-lithio-2-bromothiophene afforded α,ω-bis(5-bromo-2-thienyl)oligo(dimethylsiloxane), which underwent the Stille coupling reaction with bis(tributylstannyl)dibutylquinquethiophene to give an oligo(dimethylsiloxane)-heptathiophene alternate polymer. Spin-coated films of the heptathiophene polymer showed semiconducting properties in the thin film transistor system after the device was annealed at 60 °C. Examination of the film morphology by AFM revealed microphase separation that affected the transistor activity.