Effect of Aromatic Co‐Solvents on the Efficiency of Atom Transfer Radical Coupling Reactions of Fluorinated and Non‐Fluorinated Vinyl Aromatic Polymers

Monobrominated versions of poly(pentafluorostyrene) (PPFSBr), polystyrene (PSBr), and poly(methyl acrylate) (PMABr) are prepared by atom transfer radical polymerization (ATRP) and employed in a variety of atom transfer radical coupling (ATRC)‐type reactions to observe the impact of external aromatic faces on the extent of coupling (Xc). In ATRC reactions assisted with the radical trap 2‐methyl‐2‐nitrosopropane (MNP), Xc is nearly unchanged when the electron‐rich benzene co‐solvent (50% v/v with THF) is replaced with the electron‐poor hexafluorobenzene (HFB) for PSBr and PMABr. In the case of PPFSBr, the addition of benzene to the reaction mixture results in far lower extents of coupling (Xc < 0.2). 1H NMR spectra of the radical trap MNP in HFB show greater aggregation to the inactive form, compared to the spectra obtained in benzene. To remove the effect of the radical trap interacting with the aromatic co‐solvent and altering the rate of coupling, traditional ATRC reactions are performed with the same co‐solvent systems and, in this case, HFB results in higher Xc values across all polymer types. This is consistent with HFB pushing the position of the KATRP further toward the active radical, while benzene increases the reactivity of the MNP radical trap. The addition of aromatic faces in atom transfer coupling reactions is found to alter the extent of coupling by altering both KATRP and the reactivity of the radical trap. Electron‐rich faces, such as benzene, increase the reactivity of the radical trap 2‐methyl‐2‐nitrosobenzene, while the electron‐poor hexafluorobenzene shifts the KATRP further toward the active radical.