Fluorene homopolymers and copolymers

We report our progress in the preparation of a variety of high molecular weight polymers based on fluorene ring system. A portfolio of fluorene-related homopolymers and copolymers has been developed through Suzuki coupling of 9,9-disubstituted 2,7-bis-1,3,2-dioxaborolanyl-fluorene with a variety of aromatic dibromides. In the case of fluorene homopolymers, the polyphenylene (PP) main chain provides the mechanical, electrical as well as the electronic properties while the presence of carbon-9 forces the phenyl rings to be in plane resulting in improved conjugation. Additionally, carbon-9 provides a site for polymer property modification without altering effective conjugation. In the case of alternating polymers, the optical and electronic properties of the polymers are tailored through selective incorporation of different aromatic units into the system. These polymers are soluble in common organic solvents and are readily processed into thin films of high quality by spin casting. Unlike light emitting diodes (LEDs) based on poly(phenylenevinylene) (PPV) and related materials which have holes as the majority carriers, devices with fluorene polymers appear to have electrons as the majority carrier and their performance is markedly improved when modified with an appropriate polymeric hole transporting layer. Red and green devices have shown lifetimes exceeding 1000 h at a brightness of 150 cd/m2 with minimal voltage change.