Radical cyclopolymerization of divinyl acetals—structure variation with polymerization conditions

Radical polymerizations of divinyl formal, acetaldehyde divinyl acetal, and acetone divinyl acetal were conducted under a series of conditions, and the microstructures of the cyclopolymers obtained were examined by ¹H NMR and ¹³C NMR spectroscopies. The cyclopolymers contained cis-dioxolane units as the major structure along with other minor structures such as the pendant dioxolane unit and trans-dioxolane unit. The content of the major structure increased with lowering polymerization temperature and increasing monomer concentration. The uncyclized unit and the six-membered dioxane ring were not formed under any condition. The propagation steps included cyclization and isomerization in addition to monomer addition and are discussed on the basis of variation in polymer structure with polymerization conditions. The methyl substitution at the acetal carbon lowers isomerization of the cyclized radical.