Starch was partially acetylated by acetic anhydride in the presence of pyridine and N

N-dimethylformide (DMF)

which was used as an activator

and starch acetate (St-Ac) with substituting degree (DS) about 0.7～1.9 was obtained．The effect of the solvating time by DMF and quantity of acetic anhydride on DS was studied．Graft polymerization of ε-caprolactone (ε-CL) onto starch acetate was carried out through anionic ring-opening polymerization of ε-CL in diethylene glycol dimethyl ether solution．The graft polymerization was initiated by—ONa groups which were formed through the reaction of the remained—OH groups in St-Ac with naphthalene sodium (NS)．The grafting reaction was characterized by grafting percentage

monomer conversion

as well as gel permeation chromatography (GPC) through comparison of the Mn

Mwand Mw／Mn of St-Ac with that of the grafted copolymer

starch grafted polycaprolactone (St-g-PCL)．The influence of the reaction temperature

monomer and NS concentrations on the grafting percentage and the monomer conversion was discussed．The results showed that the grafting percentage and the monomer conversion vary in a way of S curves as grafting temperature increased from 50℃ to 150℃

but increase with the increasing of the monomer concentration and NS concentration．