Novel blue-light-emitting truxene-containing hyperbranched and zigzag type copolymers: Synthesis, optical properties, and investigation of thermal spectral stability

Two series of novel alternating polyfluorene copolymers containing 10,15-dihydro-5H-diindeno[1,2-a;1',2'-c]fluorene (truxene) moiety have been prepared through the Pd(0)-catalyzed Suzuki polymerization. The structure and purity of desired polymers is fully characterized by H-1 and C-13 NMR, UV-vis, and photoluminescent spectroscopy, gel permeation chromatography, elemental analyses, and TGA/DSC. The absorption and PL spectra of all polymers both in solutions and in thin films exhibit similar behaviors. For example, in solutions, the absorption spectra peak at about 360 nm, and the PL spectra show a maximum at about 390 nm with a shoulder at 412 nm. The introducing of the truxene moiety into polyfluorene and the hyperbranched and zigzag type molecular structures significantly reduce aggregation formation and enhance the thermal spectral stability of the desired polymers. They exhibit good solubility in common organic solvents as well as facile film forming properties. Bright blue emission is observed in both solution and solid states under UV excitation. The investigation of thermal spectral stability reveals that the long-wavelength emission upon thermal treatment usually observed in polyfluorene has been effectively reduced in our polymers.