Atom transfer radical polymerization by [RuCl2(PPh3)2(amine)] catalysts: Cyclic amines as tuner of reactivity

Atom transfer radical polymerizations (ATRP) of styrene (St) and methyl methacrylate (MMA) mediated by [RuCl2(PPh3)2(amine)] complexes, with amine = pyrrolidine (1), piperidine (2), or perhydroazepine (3), were investigated as a function of time, temperature, and concentrations of monomers and 2-bromoisobutyrate as initiator. The plots of ln([M]0/[M]) vs. time and molecular weights vs. monomer conversion were linear and the dispersity indexes decreased with increasing monomer conversions. The complexes 1, 2, and 3 were able to mediate the polymerizations with acceptable rate and level of control. Differences in the rate and control of polymerization were observed in the order 3 > 2 > 1 for both monomers. The activities were discussed considering the steric hindrance and electronic characteristics of the amines as ancillary ligands in the metal centres, considering studies by cyclic voltammetry and NMR.