Synthesis of poly(9‐hexyl‐3,6‐carbazolyleneethynylene) and its model compounds

The novel conjugated polymer poly(9‐hexyl‐3,6‐carbazoylyleneethylene) ( 16 ) was prepared by palladium‐catalyzed polycondensation of 3,6‐diiodo‐9‐hexylcarbazole and 3,6‐diethynyl‐9‐hexylcarbazole. The polymer has a number‐average molecular weight ( M̄ n ) of 3 100. By fractionation a polymer with M̄ n of 6 400 was obtained. Besides polycondensation, a palladium‐catalyzed bond‐opening polymerization of the triple bonds occurs as a side reaction which can be partially suppressed by lowering the reaction temperature to 60°C. Two well‐defined model compounds of the title polymer, a dimer and a trimer, were synthesized by stepwise reaction. The mass spectra of both model compounds demonstrate the remarkably high stability of the radical cations of the dimer and trimer. Since the trimer forms a stable glass it is ideally suited for the investigation of its photoconductive properties. First experiments carried out by the Time‐of‐Flight technique showed remarkably high carrier mobilities up to 2 · 10 −4 cm 2 /(V · s) for the trimer.