The ring-opening copolymerization of methyl ethylene phosphate (MEP, 2-methoxy-2-oxo-1,3,2-dioxaphospholane) and e-caprolactone (CL) was performed in bulk with lanthanum tris(2,6-di-tert-butyl-4-methylphenolate)s as single-component catalyst, resulting in poly(ester-phosphoester) random copolymers with high molecular weight and moderate molecular weight distribution. The properties of the copolymers were characterized by differential scanning calorimetry, X-ray diffractometer, dynamic mechanical analysis, and static water contact angle measurement. The crystallinities of the copolymers were reduced with the increase of MEP molar fraction in the products. Moreover, copolymers with enhanced hydrophilicity and lower glass transition temperature could be obtained with higher MEP content, which may provide potential applications in biomedical field. (C) 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 49: 4987-4992, 2011