Synthesis and free radical polymerization of four alkyl substituted six-membered cyclic ke-ten ascetals; 4-methyl-2-methylene-l

3-dioxane (II)

4

6-dimethyl-2-methylene-1

3-dioxane (IV)

5

5-dimethyl-2-methylene-1

3-dioxane (VI)

and 5

5-diethyl-2-methylene-1

3-dioxane (VIII) have been studied. Results indicated that introduction of methyl or ethyl substituents into β-position of oxygen atom in ring slightly effected ring-opening polymerization

but substituents at a-posi-tion of oxygen atom showed significant effect on the competition of polymerizations

that the ring-opening favored to form a more stable radical species. A complete ring-opening polyme-rization of (IV) was occured in a dilute benzene solution and in the presence of DTBP at 120℃ to give a polymer with polyester structure.