Basicity Can Choregraph Regeneration in Homogeneous ARGET ATRP of Styrene

There are two drawbacks in the use of H2AA when polymerizing a hydrophobic monomer such as styrene. First, the low solubility of the reducing agent in non-aqueous solvents. Second, the reduction kinetic rate constant of the catalyst by H2AA is around two-orders of magnitude lower than that of ascorbate (HAA–). In non-dissociating solvents this means that the polymerization is much slower since it is strictly related to the amount of reduced catalyst. To overcome this, we employed for the first time a more lipophilic ascorbic acid derivative (5,6-isopropylidene ascorbic acid) in place of H2AA, complemented by nitrogen bases of varying basicity: trimethylpyridine (TMP), diisopropylethylamine (DIPEA), and 1,8-diazabicyclo(5.4.0)undec-7-ene (DBU). The resulting system is an efficient and effective, homogeneous ARGET ATRP of styrene. Furthermore, it highlighted how basicity influences the concentration of radicals, and thus control over the final product.