Partially fluorinated and perfluorinated dioxolane and dioxane derivatives have been prepared to investigate the effect of fluorine substituents on their free-radical polymerization products. The partially fluorinated monomer 2-difluoromethylene-1,3-dioxolane (I) was readily polymerized with free-radical initiators azobisisobutyronitrile or tri(n-butyl)borane-air and yielded a vinyl addition product. However, the hydrocarbon analogue, 2-methylene-1,3-dioxolane (II), produced as much as 50% ring opening product at 60 degreesC by free-radical polymerization. 2-Difluoromethylene-4-methyl-1,3-dioxolane (III) was synthesized and its free-radical polymerization yielded ring opening products: 28% at 60 degreesC, decreasing to 7 and 4% at 0 degreesC and -78 degreesC, respectively. All the fluorine-substituted, perfluoro-2-methylene-4-methyl-1,3-dioxolane (IV) produced only a vinyl addition product with perfluorobenzoylperoxide as an initiator. The six-membered ring monomer, 2-methylene-1,3-dioxane (V), caused more than 50% ring opening during free-radical polymerization. However, the partially fluorinated analogue, 2-difluoromethylene-1,3-dioxane (VI), produced only 22% ring opening product with free-radical polymerization and the perfluorinated compound, perfluoro-2methylene-1,3-dioxane (VII), yielded only the vinyl addition polymer. The ring opening reaction and the vinyl addition steps during the free-radical polymerization of these monomers are competitive reactions. We discuss the reaction mechanism of the ring opening and vinyl addition polymerizations of these partially fluorinated and perfluorinated dioxolane and dioxane derivatives. (C) 2004 Wiley Periodicals, Inc.