With CuBr/tetramethylguanidino-tris(2-aminoethyl)amine (TMG(3)-TREN) as the catalyst, the atom transfer radical polymerization (ATRP) of methyl methacrylate, n-butyl acrylate, styrene, and acrylonitrile was conducted. The catalyst concentration of 0.5 equiv with respect to the initiator was enough to prepare well-defined poly(methyl methacrylate) in bulk from methyl methacrylate monomer. For ATRP of n-butyl acrylate, the catalyst behaved in a manner similar to that reported for CuBr/tris[2-(dimethylamino)ethyl]amine. A minimum of 0.05 equiv of the catalyst with respect to the initiator was required to synthesize the homopolymer of the desired molecular weight and low polydispersity at the ambient temperature. In the case of styrene, ATRP with this catalyst occurred only when a 1:1 catalyst/initiator ratio was used in the presence of Cu(0) in ethylene carbonate. The polymerization of acrylonitrile with CuBr/TMG(3)-TREN was conducted successfully with a catalyst concentration of 50% with respect to the initiator in ethylene carbonate. End-group analysis for the determination of the high degree of functionality of the homopolymers synthesized by the new catalyst was determined by NMR spectroscopy. The isotactic parameter calculated for each system indicated that the homopolymers were predominantly syndiotactic, signifying that the tacticity remained the same, as already reported for ATRP. (c) 2005 Wiley Periodicals, Inc.