Abstract: In the presence of DMF/LiCl solvent, rosin starch ester with the degree of substitution (D_s) of 0.125 2 was synthesized by O-acylation of starch with rosin acid chloride. The target product was analyzed and characterized by means of FT-IR, solid state ¹³C NMR, XRD and SEM. The reaction conditions were studied with single factor experiments and response surface methodology. A reaction model and the optimum conditions were obained. The optimum synthesis conditions were as follows: reaction time 6.5 h, reaction temperature 95 ℃, pyridine amount 3.5 mL, activation time of starch 52.5 min, DMF 29 mL and molar ratio 1∶1 (rosin acid chloride/the hydroxyl group per D-glucose unit). Under optimal conditions, the yield of RSE and D_s were 65.89 % and 0.125 2, respectively. Furthermore, its solubility and diaphaneity were determined. The results showed that compared with the unmodified starch, the crystal linity and diaphaneity of the target product decreased, and its hydrophobicity increased.

Key words: rosin acid chloride, starch, rosin starch ester, response surface methodology