Concurrent Initiation by Air in the Atom Transfer Radical Polymerization of Methyl Methacrylate

Abstract

AbstractThe effect of air in atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) was studied. Air initiated polymerization was clearly noticed by the appearance of a low molecular weight peak in the synthesis of high molecular weight poly(isobutylene)‐graft‐poly(methyl methacrylate) (Mn = 5.0 × 105 g/mol). The concentration of chains initiated by oxygen (air) was ≈8 × 10−4 mol/L, determined using the Gladstone‐Dale relationship. The tentatively proposed mechanism for air initiated polymerization was supported by kinetic studies. Similar to typical ATRP systems, the rate of air initiated polymerization increased with temperature, [MMA], amount of air, and activity of the catalyst complex. Polymers with lower polydispersities (Mw/Mn = 1.13) were obtained in the presence of Cu(II) as compared to Cu(I) catalyst complex system.Kinetic plots for the air initiated bulk polymerization of MMA at (•) 20 °C, (▪) 50 °C, and (▴) 90 °C.magnified imageKinetic plots for the air initiated bulk polymerization of MMA at (•) 20 °C, (▪) 50 °C, and (▴) 90 °C.