Mechanism of persulfate decomposition in aqueous solution at 50°C in the presence of vinyl acetate and nitrogen

The rate of the thermal decomposition of potassium persulfate has been studied in an unbuffered aqueous solution at 50°C in nitrogen atmosphere in the presence of vinyl acetate (VA) monomer (M). It has been found that the initial rate of persulfate decomposition may be written as in the concentration range of persulfate (1.85 × 10^?2–1.85 × 10^?3 m/dm³) and VA (0.054–0.27 m/dm³). The pH of the aqueous solution of persulfate was found to decrease continuously at 50°C, but there was no measurable change of pH of the aqueous solution containing persulfate and VA at 50°C in the presence of nitrogen at the early stages of the reaction. VA, methyl acetate, and ethyl acetate have been found to undergo very slow hydrolysis in aqueous solution at 50°C. The partition coefficient (β) of the monomer between the polymer phase and the aqueous phase was found to be 21 ± 2 in the presence and absence of electrolytes (K₂SO₄, 10^?4–10^?3 m/dm³) by the bromometric estimation of the monomer present in the aqueous phase containing known amounts of monomer 1.80–2.20%, w/v] and freshly prepared polymer (0.3–0.5 g/100 mL). Above 10^?2 (m/dm³) persulfate, the polymer obtained was found to be insoluble in common solvents, viz., acetone, benzene, etc. Highly purified sodium dodecyl sulfate (0.5–5.0 × 10^?3 m/dm³) had no measurable effect on the rate of persulfate decomposition.