Poly(dendrimers) withPhosphorescent Iridium(III)Complex-Based Side Chains Prepared via Ring-Opening Metathesis Polymerization.

Phosphorescent poly(dendrimers) with a norbornene-derivedbackbonehave been synthesized using ring-opening metathesis polymerizationwith the Grubbs III catalyst. The dendrimers are comprised of a heterolepticiridium(III) complex core with two 2-phenylpyridyl ligands and a phenyltriazolylligand, biphenyl-based dendrons, and 2-ethylhexyloxy surface groups.The phenyltriazolyl ligand provides the attachment point to the polymerbackbone, and the two poly(dendrimers) differ in the number of dendronsattached to the 2-phenylpyridyl ligands. The poly(dendrimer) withone and two dendrons per ligand are termed mono- and doubly dendronized.The mono- and doubly dendronized poly(dendrimers) were found to haverelatively narrow polydispersities, around 1.4, viscosities approachingthose required for inkjet printing, and could be solution processedto form thin films. The dendrons played an important role in controllingthe photophysical properties of the materials. The parent homopolymerwith the same iridium(III) complex but no dendrons attached to theligands had a solution photoluminescence quantum yield (PLQY) of 48%.The solution PLQY was found to increase with increasing number ofdendrons with the mono- and doubly dendronized materials having solutionPLQYs of 65% and 71%, respectively. The increase in PLQY is due todecreased intrachain interchromophore interactions. A similar trendwas observed in the solid state with the parent, mono-, and doublydendronized polymers having film PLQYs of 2%, 44%, and 58%, respectively,demonstrating that both intra- and interchain interactions are controlledby the dendrons. [ABSTRACT FROM AUTHOR]