A new biodegradable starch graft copolymer, starch-g-poly(1,4-dioxan-2-one), was synthesized through the ring-opening graft polymerization of 1,4-dioxan-2-one onto a starch backbone. The grafting reactions were conducted with various 1,4-dioxan-2-one/starch feed ratios to obtain starch-g-poly(1,4-dioxan-2-one) copolymers with various poly(1,4-dioxan-2-one) graft structures. The microstructure of starch-g-poly(1,4-dioxan-2-one) was characterized in detail with one-and two-dimensional NMR spectroscopy. The effect of the feed composition on the resulting microstructure of starch-g-poly(1,4-dioxan-2-one) was investigated. (C) 2004 Wiley Periodicals, Inc.