Preparation and luminescence properties of polypyrrole-thiophene derivatives

Four kinds of polypyrrole-thiophene derivatives (PPy-Th) are prepared via solution polycondensation using pyrrole, 3-acylpyrrole, and 2-thenaldehyde as monomers. The structure, molecular weight, micromorphology, thermal degradation, ultraviolet-visible absorption, and luminescence performance of the derivatives are investigated by fourier transform infrared (FTIR), hydrogen nuclear magnetic resonance (¹HNMR) spectroscopy, gel permeation chromatography (GPC), X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), ultraviolet-visible (UV-Vis), and fluorescence spectra. FTIR and ¹HNMR confirm that the derivatives have been successfully fabricated, and GPC indicates that the derivatives belong to oligomers with narrow molecular weight distribution. For acyl-substituted derivatives, the microstructures are mainly lamellar accumulation. Furthermore, under ultraviolet excitation, the derivatives can produce blue or green light emission, corresponding to the transitions of large π electrons in the conjugated structure of the molecular chains. Especially, the maximum emission wavelengths and Stokes shifts of the acyl-substituted derivatives are markedly larger than that of the non-acyl-substituted derivatives. The fluorescence quantum yield and band gap of the PVT are 4.46% and 2.01 eV, respectively. The fabricated PPy-Th can be used as luminescent materials in the development and application of polymer light-emitting diodes.