Carboxyl-terminated poly(vinyl alcohol). Chain transfer of methyl propionate to vinyl acetate

Poly(vinyl acetate) was prepared at 60°C with benzoyl peroxide by using methyl[carbonyl-¹⁴C] propionate as chain transfer agent and solvent. The resulting polymer was hydrolysed to poly(vinyl alcohol) (PVAL) having carboxyl end groups and the average number of carboxyl groups per chain was unambiguously determined by comparing the activity of the polymer to that of the methyl propionate. An average density of 1,5 carboxyl groups per chain was found for poly(vinyl alcohol) prepared from poly(vinyl acetate) of DP 80 – 90. Other methods of end group analysis for carboxyl groups in PVAL are discussed.