Synthesis by oxidative polymerization with FeCl3 of a fully aromatic twisted poly(3,6-carbazole) with a blue-violet luminescence

Oxidative polymerization of 1,4,5,8,9 pentamethylcarbazole with FeCl3 in chloroform solution, yields a new electroactive well-defined poly(3,6-carbazole) with a twisted structure due to steric hindrance of the adjacent monomer units. This non-coplanar structure allows, for the first time, to a carbazole compound to be converted in high polymer by the dehydrocoupling route using FeCl3 as the oxidizing agent. Soluble materials with molecular weights Mw around 104, high glass transition and thermal stability in air, were obtained. Electrochemical studies of polymer films exhibited one irreversible oxidation process at high potential consistent with a non-conjugation between the carbazole moities. Moreover, deviation from the coplanarity of consecutive rings of poly(1,4,5,8,9-pentamethyl-3,6-carbazolylene) permits these materials to emit a bright pure blue-violet light with no excimer formation, which can be interestingly used for the development efficient light-emitting diodes.