On the Termination Mechanism in the Radical Polymerization of Acrylates

In a recent publication, Nakamura and co-workers studied the termination mechanism in the radical polymerization of acrylates. Contrary to conventional thinking, their conclusion is that termination is overwhelmingly by disproportionation. This finding impacts on a large body of the previous work in the polymerization of acrylic monomers which this work seeks to address. Analysis of the molecular weight distribution of acrylic polymers obtained under different polymerization conditions shows that termination by combination is the more probable mechanism for mutual termination of secondary radicals. It is proposed that in the experiments conducted by Nakamura and co-workers, backbiting plays a key role and their experimental data are reinterpreted, showing that they are more revealing with respect to the mode of termination of the midchain radical produced by backbiting, than to bimolecular termination of secondary radicals.