Blue photoluminescence N-substituted poly(4H-benzo[def]carbazole)s

• New poly(carbazole)s having 4,5-ethenylene and ethylene bridges were synthesized.
• The polymers had appropriate Mn, solubility, and Φf to be applied in emissive devices.
• Poly(2,6-benzocarbazole)s had appropriate band gap for blue-light emitting.
• Poly(1,7-benzocarbazole) had narrower band gap than the 2,6-linked ones.

N-Alkyl and N-phenyl substituted poly(carbazole)s having a 4,5-ethenylene bridge, poly(4H-benzo[def]carbazole)s, were newly synthesized. Poly(carbazole)s having a 4,5-ethylene bridge were also synthesized for comparison. They were prepared from corresponding dibromo monomers by Ni(0)-catalyzed Yamamoto polycondensation. All the polymers had good solubility in common organic solvents, enough high molecular weights to make thin films, and good thermal stability showing about 400 °C of temperature at 5 wt% loss in TGA. The band gaps of these polymers were in the range of 2.77–3.15 eV which were appropriate for bluish light emissions. The absorption and emission maxima of these polymers in CHCl3 were in the ranges of 361–396 and 419–456 nm, respectively. These polymers showed good fluorescence quantum efficiencies in CHCl3. The energy levels of highest occupied molecular orbital of the poly(benzocarbazole)s were shallower than those of corresponding 4,5-ethylene bridged poly(carbazole)s.

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