Light Emitting Properties of Fluorine-Substituted Poly(1,4-phenylene vinylenes)

Three fluorine-containing polymers, poly(2-fluoro-1,4-phenylene vinylene), poly(2,5-difluoro-1,4-phenylene vinylene), and poly(2[5]-( n -hexyloxy)-5[2]-fluoro-1,4-phenylene vinylene) ( 1 − 3, respectively) have been synthesized by the soluble precursor method and were used to fabricate light emitting diode (LED) devices. Monosubstituted 1 yielded an electroluminescent emission peaking at 560 nm (green-yellow); polymers 2 and 3 emitted in the 600−610 nm region (red). The result for 1 represents a blue shift in emission relative to emission from hompolymeric unsubstituted poly(1,4-phenylene vinylene) (PPV) LEDs fabricated by similar techniques, while the results for 2 and 3 represent a substantial red shift. These results may be compared to those obtained from LEDs fabricated from copolymers of PPV and poly(2,3,5,6-tetrafluoro-1,4-phenylene vinylene), which show a slightly blue shifted emission relative to 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 et al . is attributed to the fact that EL emission from 1 − 3 reflects the electronic effects of fluorine substitution upon the EL spectra, whereas the work of Benjamin et al . demonstrated the effects of changes in the average chain length of EL emitting homo-PPV blocks in PPV- co -PPVF4 copolymers.