New polyquinoline copolymers: Synthesis, optical, luminescent, and hole-blocking/electron-transporting properties

A series of polyquinolines containing the 9,9-di-n-hexylfluorene unit in the main chain were synthesized via Friedlander quinoline synthesis in good yields. The thermal, optical, luminescent, electrochemical, and hole-blocking/electron-transporting properties of these polyquinolines were examined. The glass transition temperatures (T-g) were in the range 195-243 degrees C, and these polyquinolines had initial decomposition temperatures of >388 degrees C. Their optical and luminescent properties varied with the chain rigidity and conjugation length. Cyclic voltammetry studies reveal that these polyquinolines undergo irreversible oxidation onset around -6.0 eV, and their LUMO level ranged from -2.78 to -3.21 eV. The application of two of these polyquinolines as a hole-blocking/electron-transporting layer in polymeric LEDs was demonstrated.