Novel deep blue fluorescent fluorene-based copolymer containing hole-transporting arylamine segments

A novel conjugated copolymer-poly((9,9-dioctylfluorene)-alt-(N,N′-diphenylbenzidine)), bearing an arylamine moiety in the polymer backbone, has been synthesized by a modified Ullmann reaction. The new polymer can be easily dissolved in common organic solvents and form uniform thin films. The NMR and FT-IR spectra showed that it has a well-defined structure. Thermogravimetric analyses and differential scanning calorimetry analyses indicated that the polymer exhibits good thermal stability with the onset decomposition temperature in nitrogen at 300 °C and a glass-transition temperature (T_g) at 148 °C. The UV and photoluminescence spectra of the film samples indicate that the polymer has a band gap of 2.83 eV and deep blue light-emission. Cyclic voltammetry illustrated that the polymer can be reversibly p-doped and dedoped at rather low oxidative potential compared with poly(dialkylfluorene), implying that the new polymer has better hole-transporting property. All the results demonstrate that the obtained polymer is a promising deep blue light emission or hole-transporting material for PLED applications.