A polyfluorene 12 has been prepared in which bulky polyphenylene dendrimer substituents suppress formation of long wavelength emitting aggregates, thus giving a polymer with pure blue emission. Absorption- and emission spectra and molecular modeling confirm that the bulky dendrimer side chains do not cause extra torsion between the fluorene units. New polyfluorenes with 9,9-diaryl substituents have been prepared to determine the minimum size of substituent necessary for aggregation suppression. An LED using 12 has been demonstrated to produce blue emission with onset voltages below 4 V.

702.[22] The optical properties of the composites were dependent on the fraction of chiral dopant. The 11.5 wt.-% fraction reported here is for a composite that was amongst the best in terms of transparency and isotropy in our experiments. Detailed results of the dependence of the optical properties of the composites on the chiral dopant fraction will be reported elsewhere.

There is increased interest in developing multicolor light-emitting devices. We report here the fabrication and study of multilayer color-variable/white light-emitting devices based on pyridine-containing conjugated polymers and para-sexiphenyl (6P) oligomer. Voltage-dependent multicolor emission was observed in both bilayer and trilayer configurations. The emission colors of single devices cover a wide range of visible spectra whose Commission International de I’Eclairage (CIE) color coordinates vary from blue to white to green with increasing voltages. The color coordinate traverses along a straight line in the CIE chromaticity diagram. The role of interfaces in the operation of devices is discussed.

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