To improve efficiency, processability, and stability, three novel poly-(pphenylene
vinylenes) (PPVs) derivatives (Pa, Pb, and Pc) with pendent 2,4-difluorophenyl
and fluorenyl moieties were synthesized via Gilch reaction. Their structures
were characterized by 1H NMR, 13C NMR, and ELEM. ANAL. Compared with those of PPV and MEH-PPV, the absolute quantum efficiencies of these polymers showed remarkable improvement (measured at 38.7, 37.2, and 20.3%, respectively), which can be attributed to the presence of twisted multiaryl segments and fluorine atoms. TGA revealed that the inflection temperatures of their thermal decomposition curves were above 400
C. Double-layered electroluminescent devices with these polymers as light-emitting layers  ITO/PEDOT:PSS/Polymer/Ba/Al] showed peak emissions at
493/515, 503, and 600 nm and maximum luminance of 2700, 450, and 4700 cd/m2 for Pa, Pb, and Pc, respectively, with onset voltages of 4 V.