Activator Generated by Electron Transfer for Atom Transfer Radical Polymerization

A novel procedure was developed for activation of an oxidatively stable catalyst complex added to an atom transfer radical polymerization (ATRP). Tin(II) 2-ethylhexanoate (Sn(EH) 2 ) was used as a reducing agent of various Cu(II) complexes in ATRP of various monomers initiated by alkyl halides. This approach further improves a simultaneous normal and reverse initiation (SR&NI) by eliminating free radical initiators for the activation of the higher oxidation state catalyst complex. As a result, “activator generated by electron transfer” (AGET) ATRP allows the preparation of pure block copolymers. Several combinations of monomer/catalyst complex precursor were studied, including styrene/CuCl 2 /dNbpy, octadecyl methacrylate/CuCl 2 /dNbipy, methyl methacrylate/CuCl 2 /PMDETA, n -butyl acrylate/CuBr 2 /PMDETA, and methyl acrylate/CuCl 2 /Me 6 TREN. Polymerization proceeded in a controlled way for all systems, producing well-defined polymers with controlled degree of polymerization and narrow molecular weight distribution, demonstrating the robust nature of AGET ATRP. Additionally, Sn(EH) 2 was used simultaneously as a reducing agent for ATRP of octadecyl methacrylate and a catalyst for ring-opening polymerization (ROP) of ε-caprolactone, allowing direct synthesis of the corresponding block copolymer.