Synthesis and Characterization of Eumelanin-Inspired Poly(indoylenearylenevinylene) s and Poly(indoylenearyleneethynylene)s

Four novel conjugated polymers containing the eumelanin-inspired indole core have been successfully synthesized using common cross coupling reactions. These polymers differed by the arylene and the carbon-carbon bond linkage. Optoelectronic experiments of these polymers suggest that the ethynylene linkage contributed to the red-shifted absorption spectra and blue-shifted emission spectra when compared to the vinylene linkage polymers. Furthermore, the optical bandgaps of the poly(indoylenearyleneethynylene) s (PIAEs) were smaller compared to the poly(indoylenearylenevinylene) s (PIAVs). Surprisingly, the HOMOs of these polymers were less affected by the nature of the carbon-carbon linkage. However, the LUMOs of the PIAEs were lower in comparison to the PIAVs. These eumelanin-inspired PIAEs and PIAVs are good fluorophores with fluorescence quantum yields ranging from 0.12 to 0.67 and have good thermal stability for applications such as in organic light-emitting diodes. (C) 2016 Wiley Periodicals, Inc.