A new series of 2,2‘-(9,9-dioctyl-9H-fluorene-2,7-diyl)diacetonitrile-based alternating polyfluorene
copolymers (P12
-
FL, P13
-
FL, P14
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FL) containing ortho-, meta-, and para-substituted phenylene derivatives
have been designed, synthesized, and characterized. These polymers were synthesized using a Knoevenagel
condensation polymerization reaction and were found to be predominantly in the trans configuration. The resulting
polymers were found to be thermally stable and readily soluble in common organic solvents. The structural,
configurational, and conformational changes in the backbone caused a wide variation in the absorption and emission
maxima of the polymers. The fabricated light-emitting devices showed very good performance in terms of turn-on voltage, electroluminescence, and lifetime properties.
Devices with varying concentrations of singlewalled carbon nanotubes (SWNTs) dispersed in three derivatives of poly(p-phenylene vinylene) are prepared, and their electroluminescent properties evaluated. Increasing the concentration of SWNTs improves the electrical conductivity of the nanocomposites. However, an undesired increase in the electroluminescence (EL) turn-on voltage is observed for the hybrids, possibly due to photoluminescence quenching of excitons by the SWNTs. At relatively low concentrations of SWNTs, there is an increase in the EL lifetime; in contrast, at relatively high concentrations of SWNTs, due to photoluminescence quenching by the nanotubes, significant reduction in brightness and faster degradation of the EL performance of the devices is observed.
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