Amorphous poly-2,7-fluorene networks

We have developed a novel strategy for the synthesis of emitters, based on amorphous poly-2,7-fluorene (2,7-PF) networks which exhibit high glass tran sition temperatures and good photoluminescence properties and are suitable for incorporation into multilayer light-emitting diodes (LEDs). The materia ls design includes nickel(0)-mediated copolymerization of 2,7-dibromo-9,9-d ihexylfluorene with a tetrafunctional spiro-compound, 2,2',7,7'-tetra-bromo -9,9-spirobifluorene, and 4-bromostyrene as end-capping reagent. The introd uction of the spiro-bifluorene leads to a 90 degrees branch of the growing 2,7-PF chain, the number of which can be controlled via the feed ratio of m onomers used. The termination of the growing network with 4-phenylethenyl e nd groups limits the molecular weight, hence keeps the material soluble and processable. The oligomer solution can be cast into thin films and thermal ly cross-linked leading to new amorphous 2,7-PF networks. The amorphous 2,7 -PF networks were incorporated in bilayer and trilayer LED devices which em itted colorfast blue light.