Biodegradable copolymers of 2-methylene-1,3-dioxepane (MDO) and styrene (ST) were synthesized by free-radical copolymerization using di-t-butyl peroxide (DTBP) as the initiator. The copolymers containing ester units were characterized by Fourier transform infrared (FTIR), H-1-NMR, and C-13-NMR spectroscopy. Their molecular weight and polydispersity index were determined by gel permeation chromatography (GPC). In vitro enzymatic degradation of poly(MDO-co-ST) was performed at 37 degrees C in phosphate buffer solution (PBS, pH = 7.4) in the presence of Pseudomonas lipase or crude enzyme extracted from earthworm. The experiment showed that incorporating ester units into C-C backbone chain of polystyrene would result in a biodegradable copolymer. (c) 2006 Wiley Periodicals, Inc.