Telechelic poly(1,3-dioxolane) (PDXL) bis-macromonomers bearing methyl methacrylate end groups were prepared by cationic ring-opening polymerization of 1,3-dioxolane (DXL), in the presence of methacrylic anhydride, catalyzed by Maghnite-H+ (Mag-H+), in bulk and in solution. Maghnite is a montmorillonite sheet silicate clay, which exchanged with protons to produce Mag-H+. The influence of the amount of Mag-H+, monomer (DXL), and methacrylic anhydride on monomer conversion was studied. The polymerization yield and the molecular weight of alpha,omega-bis-unsaturated PDXLs prepared depend on the amount of Mag-H+ used and the reaction time. (c) 2005 Wiley Periodicals, Inc.