Synthesis of starch-g-lactic acid copolymer with high grafting degree catalyzed by ammonia water

• The starch-g-lactic acid copolymer was synthesized by one-step in a mild condition.
• The urea was used as activating agent in the gelatification of starch.
• The non-toxic and easily obtained ammonia water was used as catalyst.
• The optimal grafting degree of starch reached 58.9%.

The study of starch-g-lactic acid copolymer has gained much attention for its completely degradable property, but its intricate synthetic procedure and low graft degree inhibited its further application. In this work, the synthesis of starch-g-lactic acid copolymer was attempted via the catalysis of ammonia water by one-step process, and the structure of starch-g-lactic acid copolymer was characterized by means of IR, 13C NMR and HMBC. The synthetic conditions were optimized as follows, the starch was activated for 2 h at 80 °C at first, starch and lactic acid with weight ratios of 1:4 reacted for 4 h at 90 °C in vacuum. The starch-g-lactic acid copolymer can be finally obtained with graft degree of starch 58.9%.