Synthesis and characterization of poly(1,4-phenylenevinylene) derivatives containing liquid crystalline oxadiazole groups



Two novel poly(1,4-phenylenevinylene) (PPV) derivatives containing liquid crystalline oxadiazole side chains were prepared by a dehydrochlorination process. The homopolymer poly(2-methoxy-5-((2-methoxy-phenyl)-5-hexyloxy-phenyloxy-1,3,4-oxadiazole)-1,4-phenylenevinylene) (HO–PE6) is insoluble in common solvents, whereas the copolymer poly(2-methoxy-5-((2-methoxy-phenyl)-5-hexyloxy-phenyloxy-1,3,4-oxadiazole))-(2-methoxy-5-(2′-ethylhexyloxy))-1,4-phenylenevinylene) (CO–PE6) is soluble in common solvents such as chloroform, THF, and p-xylene. The molecular structure of CO–PE6 was confirmed by FTIR, 1H-NMR, UV–vis spectroscopy, and polarized light microscopy. CO–PE6 showed a maximum emission at 556 nm in chloroform and at 564 nm in solid film, when excited at 450 nm. The maximum electroluminescence emission of the device indium–tin oxide (ITO)CO–PE6/Al is at 555 nm. The turn-on voltage of LEDs based on CO–PE6 and MEH–PPV is 6.5 and 8.5 V, respectively. The electron mobility of CO–PE6 is higher than that of MEH–PPV based on the results of current–voltage and electrochemical behavior of both MEH–PPV and CO–PE6. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 396–403, 2004