Ullmann coupling for low-cost synthesis of anthracene-based polyfluorenes: A photophysical approach

A set of anthracene containing polyfluorenes (PFs) having 9,10-diphenylanthracene with alkyl substituents and aniline containing fluorenes were prepared. Commonly, light-emitting polymers were synthesized using expensive palladium-like catalysts. In the present work, palladium was replaced by copper as a cost-effective PF synthesis catalyst, which is also suitable for large-scale polymer synthesis. Synthesized PFs emit light in the blue region with a bandgap of 2.87-2.90 eV. Thermally stable PFs had a decomposition temperature of more than 305 degrees C and a glass transition temperature of 125-138 degrees C. PFs were soluble in organic solvents and had a molecular weight of around 21,700-25,500. The electrochemical study of these PFs showed low level of highest occupied molecular orbital (HOMO) energy of -5.16 to -5.26 eV, which was significantly higher than that of PF (5.7 eV). These findings suggested that the resulting PFs could be used as a component of the light-emitting diode.