Synthesis and properties of polyfluorenes with phenyl substituents

Two new, alkoxyphenyl-substituted polyfluorenes, poly(9,9-bis(4′-hexyloxyphenyl)fluorene) (PPF-1) and poly(9,9-bis(4′-hexyloxyphenyl)fluorene-alt-9,9-bis(4′-(2″-(2″′-methoxyethoxy)ethoxy)phenyl)fluorene) (PPF-2), were synthesised using the Suzuki coupling reaction. The polymers were designed to obtain stable and efficient materials for light-emitting applications. Both polymers exhibit high PL-efficiencies and show PL- and EL-emission in the blue spectral region, with emission maxima in a narrow range around 427 nm. Annealing (200 °C, 2 h) of polymer films exposed to normal indoor light in ambient atmosphere, results in an additional emission band at higher wavelengths, indicating degradation by photo oxidation.