Distribution of end groups and comonomer of the acrylonitrile‐vinyl acetate copolymer

The number average molecular weight and strong acid end groups (SAG) of fractionated polymers were measured for the acrylonitrile‐vinyl acetate copolymers (93:7 in weight), which were prepared by continuous polymerization in aqueous medium with the persulfate‐bisulfiteion redox system. Average number of SAG per polymer molecule was nearly 1 for fractionated portions of the polymers prepared under the polymerization conditions of water/monomer ratio in the range 4.0–2.5 in weight. No marked difference existed in comonomer content in fractions of these polymers. For unfractionated polymers prepared under the conditions of water/monomer ratio varied from 4.0 to 1.75, average number of SAG was roughly 0.8–1. The proportion of sulfoxy end groups to SAG was estimated to be roughly from 0.5 to 0.6 and increased slightly with increased bisulfite/persulfate ratio. Based on the above results, disproportionation and transfer to bisulfite‐ion are considered to be the main processes of termination of polymer radicals in the studied range of polymerization conditions.