n-type copolymers with fluorene and 1,3,4-heterodiazole moieties

The successful realization of n-channel field-effect transistors requires the application of semiconducting polymers with high electron mobility (n-type). However, reports on n-type polymers are rather scarce in the literature. Therefore, the development of polymers with suitable electron transport properties is particularly challenging for the synthetic chemistry. Main chain polymers with strong acceptor units, such as 1,3,4-heterodiazoles, are potential candidates for electron transport materials in electronic devices. The fluorene unit is another ring system with interesting physical and chemical properties, which is often used in rigid-rod, main chain polymers. The present work introduces the synthesis of organo-soluble copolymers consisting of alternating fluorene-, 1,3,4-heterodiazole, and, in some cases, additional 2,5-dialkoxyphenylene units in the main chain. The reported synthesis involves modified classical polycondensation as well as the tetrazole route. We demonstrate the possibility of exchanging oxygen in the heteroaromatic ring with sulfur using Lawesson's reagent during the ring closure reaction. An alternative structure of the heterocyclic ring with N-phenyl in the oxygen position is feasible using the tetrazole synthetic route. The chemical and electrochemical properties of the copolyfluorenes are investigated in detail. Some of the synthesized copolyfluorenes have also been used for the preparation of "electron-only" devices enabling the calculation of the electron mobilities. Further, an organic field-effect transistor (OFET) characteristic was shown. [GRAPHICS]