AGET and SARA ATRP of styrene and methyl methacrylate mediated by pyridyl-imine based copper complexes

Two pyridyl-imine ligands, N,N-dimethyl-N′-((pyridin-2-yl)methylene)-ethane-1,2-diamine (paenMe2) and N,N-diethyl-N′-((pyridin-2-yl)methylene)-ethane-1,2-diamine (paenEt2), have been applied to AGET and SARA ATRP of styrene and methyl methacrylate. The polymeric products showed a narrow molecular weight distribution (Mw/Mn = 1.16–1.28) and a molecular weight that not only increased linearly with monomer conversion (>70%) but also matched to the theoretical value. The performance of CuII(paenMe2)Br2 and CuII(paenEt2)Br2 in AGET ATRP was almost the same and thus the steric effect between these two complexes was not significant. The activation rate constant (kact) of CuI(paenMe2)Br with PEBr was measured as 7.96 × 10−3 M−1 s−1 and the deactivation rate constant (kdeact) was estimated as 2.8 × 105 M−1 s−1. This kinetic measurement indicated that the improved control efficiency of pyridyl-imine based catalysts in AGET and SARA ATRP should be attributed to the high deactivator/activator (CuII species/CuI species) ratio that relatively enhanced the deactivation rate and lowered the radical concentration to minimize the influence of radical termination and other side reactions.