Endgroup studies in persulfate-initiated vinyl polymer by dye techniques. Part I. Initiation by persulfate alone

Abstract

Quantitative determination of endgroups of poly(methyl methacrylate), polystyrene and poly(vinyl acetate) obtained by aqueous initiation with K₂S₂O₈ under varied conditions have been made by the application of two sensitive dye techniques, called the dye partition technique and the dye interaction technique. The description of the dye techniques are given in detail. Sulfate (OSO₃^-) and hydroxyl (OH) endgroups are generally found to be incorporated in the polymers to an average total of 1.5 to 2.5 endgroups per polymer chain. Hydroxyl endgroups are always present to a fairly large extent. The proportion of sulfate endgroups in polymers is highly dependent on the pH of the polymerizing medium; it increases with the alkalinity of the medium and sharply decreases under acid conditions.