Thiocarbamide and microwave-accelerated green methylation of cassava starch with dimethyl carbonate

By combining the acceleration strategies of using thiocarbamide as a active catalyst, incorporating dimethyl carbonate (DMC) as a solvent and methylating reagent and applying microwave irradiation as energy resource, methylation of cassava starch can be performed efficiently to a high degree of substitution (DS=0.6) within 4 min. The structures of native cassava starch and methylated starch were characterized by (13)C NMR spectroscopy. Their thermal property and crystal structure were studied by thermogravimetric analysis (TG and DTG) and powder X-ray diffractometry.