Synthesis and luminescence of polyphosphazenes with carbazolyl side chains

Two new blue-light-emitting polyphosphazenes (1 and 2) containing carbazolyl groups as side chains were synthesized from a highly reactive macromolecular intermediate by a nucleophilic substitution reaction. Molecular structural characterization for the polymers was presented by ¹H NMR, IR, and ultraviolet-visible spectra, gel permeation chromatography, and differential scanning calorimetry. The polymers exhibited excellent solubility in common organic solvents and were thermally stable. A fluorescence analysis of the two materials in tetrahydrofuran showed a strong blue light emitting. The quantum yields of the polyphosphazenes were 0.55 for 1 and 0.64 for 2, relative to quinoline (in 0.1 N H₂SO₄). An electroluminescent diode was fabricated, and a bright blue light was observed; the maximum external quantum efficiency was about 0.026% at an applied forward voltage of 23 V.