The ring-opening copolymerization of ethylene carbonate (EC) with epsilon-caprolactone (CL) was carried out using neodymium. tris(2,6-di-tert-butyl-4-methylphenolate) as a single-component catalyst. Copolymers containing up to 22.0% EC contents with high molecular weights (up to 23.97 X 104) and moderate molecular weight distributions (between 1.66 and 2.03) were synthesized at room temperature. Compared with homopoly(e-caprolactone), the copolymers with EC units exhibited increased glass transition temperatures (-35.6 degrees C), reduced melting temperatures (44.5 degrees C), and greatly enhanced elongation percentage at break (2383%) based on dynamic mechanic analysis. The crystallinities of the copolymers decreased with the increasing EC molar percentage in the products. 0 (c) 2008 Wiley Periodicals, Inc.