Synthesis And Characterization Of Hyperbranched Electroluminescent Polymer With Biphenyl Structure

An A₂+B₄ approach was adopted to synthesize a series of partially conjugated hyperbranched polymer with biphenyl structure in which rigid fluorescent conjugated segments and flexible non-conjugated spacers arranged alternately through ether bonds in the skeleton. FT-IR, NMR and elemental analysis were employed to identify the structure of the monomers and polymers. TGA and DSC were employed to investigate the thermal properties of the polymers. The surface morphology of the thin film prepared from the polymer was studied via atomic force microscope (AFM).The optimized conformation of the polymer with one generation was calculated and was found to demonstrate three-dimensional structure instead of two-dimensional structure of the fully conjugated hyperbranched polymer. The end group makeup of the hyperbranched polymers with different A/B ratio, or different reaction temperatures, or different conjugated monomers, was characterized with FT-IR and the wherefores of the phenomenon was discussed in detail in the paper. It was also found that the make up of end groups had an obvious impact on the molecular weight, glass transition temperature, thermal stability and solubility of the polymers. The hyperbranched polymers with higher proportion of polar end group demonstrate higher molecular weight and glass transition temperature, better thermal stability but poorer solubility and film-forming property.Fluorescence spectrophotometer was employed to characterize the photo-luminescent property of the the polymer, including the PL spectra of the polymer with different A/B ratio, different concentration, different temperatures, and different excitation wavelength. The relative PL quantum efficiency of the polymer in dilute chloroform solution was measured. A brief LED device with configuration ofITO/PEDOT(30nm)/HP1D(80nm)/Ca(15nm)/Al(150nm) was fabricated and its performance was investigated.