Polyfluorenes with polyphenylene dendron side chains: Toward non-aggregating, light-emitting polymers

A polyfluorene 12 has been prepared in which bulky polyphenylene dendrimer substituents suppress formation of long wavelength emitting aggregates, thu s 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 su bstituent necessary for aggregation suppression. An LED using 12 has been d emonstrated to produce blue emission with onset voltages below 4 V.