A Reinvestigation of Vinyl Acetate Emulsion Polymerization: Isotope Effect

One of the most important factors in vinyl acetate polymerization is chain transfer of growing radical to the monomer ( 1 - 5 ). This was concluded because there is no dependence of molecular weight on initiator concentration. While chain transfer to polymer was found, it is unimportant below 30% conversion; there is no molecular weight increase in the polymer until higher conversions. Hydrolysis and reacetylation of low conversion polymer shows no molecular weight change, indicating that there is no back-biting on polymer acetyl groups. An interesting and to us an important question is where is the main chain transfer site on vinyl acetate. All studies concluded that the main chain transfer site was the hydrogen atoms of the acetyl group ( 6 - 9 ). Some investigators found vinyl groups in the polymer and proposed some chain transfer on the vinyl hydrogens ( 8, 9 ). On the other hand, we concluded on the basis of a kinetic analysis that