The development of poly(dendrimer)s for advanced processing

Abstract

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.

A Phosphorescent Poly(dendrimer) Containing Iridium(III) Complexes: Synthesis and Light-Emitting Properties

“…A previous report has shown that at concentrations of up to 25 mg/mL, the viscosity of a dendrimer in solution only increased by 8% relative to that of the solvent. 36 The viscosity of poly(dendrimer) 3 at various concentrations in 1,2-dichlorobenzene at 20°C is shown in Figure 3. 1,2-Dichlorobenzene was determined to have a viscosity of 1.06 cSt and at a concentration of 25 mg/mL of poly(dendrimer) 3 in 1,2-dichlorobenzene the viscosity was 1.23 cSt.…”

MALDI‐TOFMS analysis of coordination and organometallic complexes: a nic(h)e area to work in

“…Even larger porphyrin nanorings synthesised via a different method have been successfully characterised using dithranol matrix 32. The largest positive radical ions observed to date by MALDI‐TOFMS (using DCTB matrix) have been for a norbornenyl‐based homopolymer that has a dendronised iridium(III) complex attached to every monomer unit, which has an average molecular weight of 130 kDa 85. An example of a more fragile nanomaterial complex is the pentaphosphaferrocene copper(I) chloride nanospheroid,86 capable of encapsulating small molecules such as C 60 (Fig.…”

The ‘double dendron’ approach to host free phosphorescent poly(dendrimer) OLEDs

“…We have therefore focused on developing a new class of lightemitting material, namely poly(dendrimers) that have a nonconjugated backbone with dendrimer side-chains. [17][18][19][20] While polymers with small molecule iridium(III) complex sidechains [21][22][23][24][25] have been reported, the homopolymers have tended to have poor solubility 24,26 and the complexity of copolymers leads to more difficult syntheses and issues relating to reproducibility. In our first reports on phosphorescent poly(dendrimers) that were comprised of dendrimer side-chains the dendrimers were comprised of heteroleptic iridium(III) complex cores.…”