Nathalie Charton, Achim Feldermann, Alexander Theis, Martina H. Stenzel, Thomas P. Davis and Christopher Barner-Kowollik
The initiator efficiency, f, of 2,2′-azobis(isobutyronitrile) (AIBN) in dodecyl acrylate (DA) bulk free radical polymerizations has been determined over a wide range of monomer conversion in high molecular weight regimes at 60 °C. The initiator efficiency at low monomer conversions is relatively low (f = 0.13) and decreases with increasing monomer to polymer conversions. The evolution of f with monomer conversion (in high molecular weight regimes), x, at 60 °C can be summarized by the following functionality f60 °C (x) = 0.13 − 0.22 · x + 0.25 · x2 (for x ≤ 0.4). The ratio of the initiator efficiency and the average termination rate coefficient, 〈kt〉, (f/〈kt〉) has been determined at various molecular weights. The (f/〈kt〉) data may be indicative of a chain length dependent termination rate coefficient decreasing with (average) chain length, 〈i〉, proportional to 〈i〉−0.2.