Synthesis and properties of copolyarylenes containing indolo[3,2-b]carbazole moieties in the backbone

Three novel indolo[3,2-b]carbazole-based copolyarylenes were synthesized by Suzuki polycondensation of 6,12-di(4-bromophenyl)-5,11-dihydroindolo[3,2-b]carbazole with 2,5-thiophene diboronic acid, 2,5-bis(hexyloxy)phenyl-1,4-diboronic acid and 9,9-dihexylfluorene-2,7-diboronic acid bis(1,3-propanediol)ester. The molecular structure of the polymers was examined by FTIR, proton and carbon nuclear magnetic resonance spectroscopy methods. Their number average molecular weights range from 6300 to 8400gmol(-1) and polydispersity indices are in the range 1.80-2.05. Thermal properties were studied by differential scanning calorimetry and thermogravimetric analysis. The photophysical and electrochemical properties were studied by UV-vis absorption spectroscopy, fluorescence spectroscopy and electrochemical methods. The results reveal that all polymers have high thermal stability with decomposition temperatures of 328 degrees C (P1), 350 degrees C (P2) and 378 degrees C (P3) and good electrochemical properties (high HOMO energy levels, air redox stability).