Study On Lipase Synthesis Of Hydroxyethyl Starch Grafted Copolymer

Hydroxyethyl starch (HES) is a product with inducing hydroxyethyl onto starch. In this paper, hydroxyethyl starch/ε-Caprolactone grafted copolymer was synthesized by using porcine pancreatic lipase as catalyze in DMSO solution. In this reaction,ε-Caprolactone occurred open-cycle polymerization firstly and then grafted on the HES, i.e. poly(ε-Caprolactone) instead ofε-Caprolactone grafted on the HES. The structure of the copolymer was characterized by FTIR and 1H-NMR. The grafted rate of copolymer was measured by 1H-NMR and pH value titration. The effect of temperature, initial water activity, pH and the ratio of CL to HES on the grafted copolymerization was investigated. The maximum grafted rate was about 66.5%.Hydroxyethyl starch/L-lactide grafted copolymer was also synthesized by using Novozyme435 as catalyze in DMSO solution. The reaction mechanism is same with that of HES/ε-Caprolactone grafted copolymer. The structure of the copolymer was characterized by FTIR and 1H-NMR. The effect of reaction conditions on the grafted rate was studied. The maximum grafted rate was about52%.Further, the aggregation of these copolymers in water was investigated by using fluorescence spectrum, dynamic light scattering and TEM. The results indicated that the hydrophobic modified HES could assembly to micelles with hydrodynamic radius in the range of 300-800nm.