LIGHT-EMITTING PROPERTIES OF FLUORINE-SUBSTITUTED POLY(1,4-PHENYLENE VINYLENES)

Three fluorine-containing polymers, poly(2-fluoro-1,4-phenylene vinyle ne), poly(2,5-difluoro-1,4-phenylene vinylene), and poly(2[5]-(n-hexyl oxy)-5[2]-fluoro-1,4-phenylene vinylene) (1-3, respectively) have been synthesized by the soluble precursor method and were used to fabricat e light emitting diode (LED) devices. Monosubstituted 1 yielded an ele ctroluminescent emission peaking at 560 nm (green-yellow; polymers 2 a nd 3 emitted in the 600-610 nm region (red). The result for 1 represen ts a blue shift in emission relative to emission from hompolymeric uns ubstituted poly(1,4-phenylene vinylene) (PPV) LEDs fabricated by simil ar techniques, while the results for 2 and 3 represent a substantial r ed shift. These results may be compared to those obtained from LEDs fa bricated from copolymers of PPV and poly(2,3,5,6-tetrafluoro-1,4-pheny lene vinylene), which show a slightly blue shifted emission relative t o homopolymeric PPV (Benjamin, I.; Faraggi, E. Z.; Avny, Y. Davidov, D .; Neumann, R. Chem. Mater. 1996, 8, 352). The qualitative difference in EL emission for this work compared to that of Benjamin ct al. is at tributed to the fact that EL emission from 1-3 reflects the electronic effects of fluorine substitution upon the EL spectra, whereas the wor k of Benjamin ed al. demonstrated the effects of changes in the averag e chain length of EL emitting homo-PPV blocks in PPV-co-PPVF4 copolyme rs.