Electrosynthesis and characterization of water-soluble poly(9-aminofluorene) with good fluorescence properties

The electrochemical synthesis of a novel semiconducting polymer, water-soluble poly(9-aminofluorene) (P9AF), with good fluorescence properties was successfully achieved in pure boron trifluoride diethyl etherate (BFEE) by the direct anodic oxidation of 9-aminofluorene (9AF). The amino group substitution makes P9AF highly soluble in water, facilitating potential applications as a blue-light-emitting material. Fourier transform infrared spectroscopy together with theoretical calculations show that polymerization of 9AF occurs mainly at the C(2) and C(7) positions. The fluorescence spectra indicate that doped P9AF films in water are blue-light emitters with a fluorescence quantum yield of 0.44. Increasing the concentration of hydrochloric acid decreases the solubility of the doped P9AF films but increases that of dedoped P9AF films because of the different complexation of the -NH2 group on P9AF with BF3 or H+. The doped and dedoped P9AF films in 0.5 mol L-1 hydrochloric acid are blue-light emitters with fluorescence quantum yields of 0.40 and 0.17, respectively.