A norbornenyl-based homopolymer that has a dendronised iridium(III) complex attached to every monomer unit has been synthesized. The dendronised iridium(III) complex is comprised of three facially arranged 2-phenylpyridyl ligands. Two of the ligands bear first generation biphenyl-based dendrons with 2-ethylhexyloxy surface groups attached and the third ligand is attached to the polymer backbone via a benzyloxy ester. The polymer was formed by ring opening metathesis using the Grubbs III catalyst and was found to have an M p of 130 kDa by MALDI-TOF mass spectrometry. At a concentration of 25 mg cm À3 the polymer solution had a viscosity of 1.09 mPa s, which was 34% higher than a solution containing a dendrimer of same weight per volume. The dendrimer had the same core, dendrons, and surface groups but differed from the polymer in that it had dendrons attached to three of the ligands rather than the two of the polymer. The solution photoluminescence quantum yield (PLQY) of the poly(dendrimer) was found to be 57%, indicating that intra-polymer chromophore interactions were not leading to strong quenching of the luminescence. However, in the solid-state the PLQY dropped significantly, indicating that inter-polymer chromophore interactions were significant. The presence of the dendrons allowed the simple blending of the polymer with 4,4 0 -bis(N-carbazolyl)-2,2 0 -biphenyl (CBP), and the blended film had a PLQY of 50%. Simple bilayer devices with a blended emissive layer and an electron injection and transport layer had an external quantum efficiency of 6.2% at a brightness of 100 cd m À2 , showing that poly(dendrimer)s are a promising class of OLED material.

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Organic light-emitting diodes (OLEDs) have great potential for displays and lighting applications. For large area displays the ideal materials would be both phosphorescent and solution processible. These requirements mean that the materials need to be able to be patterned and the most advanced method for forming pixelated displays is inkjet printing. Light-emitting phosphorescent dendrimers have given high efficiency monochrome displays with the emitting layer deposited by spin-coating. However, the viscosity of the dendrimer solutions is insufficient for inkjet printing. We report the development of a new class of light-emitting materials, namely poly(dendrimers) in which a green emissive phosphorescent dendrimer is attached to a poly(styrene) backbone. Free radical polymerization of a dendrimer-styrene monomer gave a poly(dendrimer) with a weight average molecular weight of 24000 and a polydispersity of 3.6. A dilute solution of the dendrimer had a viscosity 15% higher than the neat solvent. Comparison of the photophysical studies of the poly(dendrimer) versus a model monomer dendrimer showed that the PL spectrum was broader and red-shifted, and the PL quantum yield around 50% lower. This was attributed to intermolecular interactions of the emissive dendrimers, which are held closely together on the polymer backbone.