The polymerization and copolymerization of a cyclic acrylate, 5-methylene-2-phenyl-1,3dioxolan-4-one (MPDO), by conventional radical polymerization and atom transfer radical polymerization (ATRP), were determined to occur by 1,2-vinyl addition according to C-13 NMR spectroscopy. Copolymerization of MPDO with methyl methacrylate (MMA) or styrene (S) led to copolymers with a much higher MPDO content than originally in the feed, suggesting high reactivity due to its captodative structure. PMPDO-PS copolymers were stable to UV irradiation and basic environments, confirming that copolymerization of MPDO also proceeded by 1,2-vinyl addition rather than ring opening. DSC heating scans of PMPDO-PMMA copolymers show a single T-g that increases with increasing MPDO content.