Free Radical Ring-Opening Polymerization of 4-n-Hexyl- and 4-n-Decyl-2-methylene-1,3-dioxolanes

Two alkyl-substituted cyclic ketene acetals, 4-n-hexyl-2-methylene-1,3-dioxolane (4) and 4-n-decyl-2-methylene-1,3-dioxolane (6), were shown to undergo free radical ring-opening polymerization with the introduction of an ester group into the backbone of an addition polymer. The spontaneous polymerization of 4 (presumable by an ionic mechanism) produced a polymer containing no ring-opened units; furthermore 4 and 6 could be stabilized with respect to spontaneous polymerization by the addition of small amounts of pyridine. On the other hand, the polymerization of 4 in a 50% (by weight) benzene solution at 110°C with di-tertbutyl peroxide as the catalyst gave quantitative ring opening to give a polyester containing both possible isomeric ring-opened units. Bulk polymerization of 4 at 60°C at 53% conversion gave 50% ring opening which was divided 31% to 19% between cleavage to give the intermediate secondary free radical and the intermediate primary radical. Copolymerization of 4 with equimolar quantities of styrene at 110°C gave at 56% conversion a copolymer consisting of 67% styrene units, 22% ester-containing units resulting from cleavage to form a secondary radical, 7% of the isomeric ester-containing units, and 4% nonring-opened units. Polymerization studies with monomer 6 gave results very similar to those obtained with 4.