Effect of Cu(II) on the kinetics of the homogeneous atom transfer radical polymerization of methyl methacrylate

The kinetics of CuBr-mediated homogeneous atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) using 2-hydroxyethyl-2-bromoisobutyrate (HEBIB) as initiator and N-(n-hexyl)pyridylmethanimine (NHPMI) as ligand was investigated. The experimental results showed that initially added Cu(II) can have strong effects on the kinetics of the ATRP depending on the [Cu(II)]0/[Cu(I)]0 ratio. When ≤10% Cu(II) relative to Cu(I) was added at the beginning of the polymerization, the kinetics can be well described by Fischer's equation (ln([M]0/[M]) ∝ t2/3).9 The obtained reaction orders for initiator, Cu(I) and Cu(II), are quite close to or the same as those in Fischer's equation, verifying the applicability of Fischer's equation in ATRP systems. On the other hand, when [Cu(II)]0/[Cu(I)]0 ≥ 0.1, the kinetics can be well interpreted by Matyjaszewski's equation (ln([M]0/[M]) ∝ t).8 The polymerization rate shows almost first order with respect to the concentrations of initiator and Cu(I) and inverse first ...