Step-ladder and ladder-type poly(para-phenylene)s approaches towards efficient blue-light emitting polymers

'Rod-coil' block copolymers with poly[2,7-(9,9-dialkyl)fluorene] (2,7-PF) b locks as the rod segment and poly(ethyleneoxide) blocks as the flexible coi l segment has been developed to combine the photophysical properties of con jugated polymers with supramolecular ordering of block copolymers. In order to balance the electron and hole injection in light-emitting devices (LEDs ), poly[2,7-(9-fluorenone)] (2,7-PFO) with low and reversible reduction pot ential (- 1.48 V) has been synthesized as electron-injection/hole-blocking material. Ladder-type poly(pam-phenylene) (LPPP) is one of the mostly favor ed materials for blue LEDs, since the polymer is fully soluble, structurall y well-defined and exhibits high photoluminescence quantum effeciency. Spec tral narrowing of the PL emission was observed at pumping pulse energies in the blue of < 5 <mu>J/pulse. LPPP films spun on a nanostructural DFB reson ator can act as single-mode blue-green solid-state lasers, so-called 'plast ic lasers'. To bridge the gap between LPPP and 2,7-PF, novel poly[2,8-(6,6, 12,12-tetraalkyl)indenofluorene]s (2,8-PIF) have been synthesized, that ex hibit an efficient blue photoluminescence and thermotropic liquid crystalli nity above 250 degreesC. (C) 2000 Academie des sciences/Editions scientifiq ues et medicales Elsevier SAS.