A dual catalyst system for atom transfer radical polymerization based on a halogen-free neutral Cu(I) complex

A neutral phenoxy-triamine copper(D complex was synthesized, and its performance as a catalyst for the ATRP of n-butyl acrylate (BA) was investigated. This halogen-free neutral cuprous complex catalyzed BA polymerization, but while the polymerization rate was high there was poor control over polymerization. The level of control over the polymerization process was improved dramatically when a small amount of a suitable copper(II) complex was added as a deactivator. Several copper(II) complexes including CuBr2, dNbpy/CuBr2, PMDETA/CuBr2, and Me6TREN/CuBr2 were investigated as deactivators. Among these deactivators, Me6TREN/CuBr2 was the most efficient at improving the level of control over the polymerization. When 3 mol % of Me6TREN/CuBr2 (versus the phenoxy-triamine copper complex) was added, the molecular weight increased linearly with conversion and agreed with theoretical values, and the polymer displayed a narrow molecular weight distribution (M-w/M-n = 1.17). The mechanism of the dual catalyst system might be similar to that proposed earlier for another binary catalyst system, the immobilized/soluble hybrid catalyst system. The high deactivation rate constant and high reducing power of Me6TREN complex might be the key properties that allow successful control over the polymerization in this dual catalyst system.