| Sumario: | Atom transfer radical polymerization (ATRP) generally requires a catalyst/initiator molar ratio of 0.1 to 1 and catalyst/monomer molar ratio of 0.001 to 0.01 (i.e., catalyst concentration: 1000–10 000 ppm versus monomer). Herein, we report a new copper-based complex CuBr/N,N,W,N'-tetrakis(2-pyridylmethyl)- ethylenediamine (TPEN) as a versatile and highly active catalyst for acrylic, methacrylic, and styrenic monomers. The catalyst mediated ATRP at a catalyst/initiator molar ratio of 0.005 and produced polymers with well-controlled molecular weights and low polydispersities. ATRP occurred even at a catalyst/initiator molar ratio as low as 0.001 with copper concentration in the produced polymers as low as 6—8 ppm (catalyst/ monomer molar ratio = 10). The catalyst structures were studied by X-ray diffraction and NMR spectroscopy. The activator CuBr/TPEN existed in solution as binuclear and mononuclear complexes in equilibrium but as a binuclear complex in its single crystals. The deactivator CuBr/TPEN complex was mononuclear. High stability and appropriate K (ATRP equilibrium constant) were found crucial for the catalyst working under high dilution or in coordinating solvents/monomers. This provides guidance for further design of highly active ATAP catalysts.
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