Abstract:

An asymmetric diacetylene derivative bearing naphthyl group, 4-(4-(4-(6-(hexyloxy)-2-naphthalen)-1-(1,3-butadiynyl))-3-vinyl-phenylethynyl)-N,N-dimethylbenzenamine, was successfully synthesized by multi-step Sonogashira reactions. The structure of the compound was confirmed with ¹H and ¹³C NMR spectroscopy and elemental analysis. Its liquid crystalline property and optical birefringence were characterized by differential scanning calorimetry(DSC), polarized light microscopy(POM) and Abbe refractometer. The absorption and emission spectra of the compound were obtained with the ultraviolet-visible absorption spectrometer and fluorescence spectrometer, respectively. The compound exhibits the nematic phase in liquid crystal state and high optical birefringence of 0.47. The peak of the photoluminescence(PL) of the compound in chloroform is at 470 nm and the quantum efficiency is 97%. The double-layer devices ITO/PEDOT/liquid crystal compound/Mg:Ag(10:1)/Ag(ITO:indium tin oxide, PEDOT:poly(3,4-ethylene-dioxythiophene thiophene)) is fabricated with a low onset voltage(6.75 V). The peak of electroluminescence(EL) is at 503 nm, and the maximum brightness value is 150 cd/m²(14.75 V). The diacetylene derivative is a promising material for liquid crystal display or organic light-emitting device.

Key words: nematic liquid crystal, high optical birefringence, high fluorescence quantum efficiency, organic light-emitting device