Effect of the Ligand in Atom Transfer Radical Polymerization Reactions Initiated by Photodimers of 9-Bromoanthracene

Slow initiation from the bridgehead radical in atom transfer radical polymerization (ATRP) reactions initiated by 9‐bromoanthracene photodimers leads to polymers' products possessing high PDI values and higher than expected $\overline M _{\rm n}$ values. We report here the effects of changing the ligand from N,N,N′,N″,N″‐pentamethyldiethylenetriamine (PMDETA) to the highly active tris[2‐(dimethylamino)ethyl]amine (Me6TREN) or tris[(2‐pyridyl)methyl]amine (TPMA) in an attempt to push the initial equilibrium further toward the initiating bridgehead radical. Overall, the ligand choice was found to add negligible control to the ATRP of styrene with any increase in the rate of initiation offset by an increase in the rate of propagation, leading to anthracene‐labeled polystyrene with similar PDI (≈1.6) and $\overline M _{\rm n}$ values regardless of the ligand choice.