An efficient and environmentally friendly method for the synthesis of cellulose carbamate by microwave heating

An efficient, solvent-free, and catalyst-free microwave synthesis of cellulose carbamate from a mixture of native cellulose and urea is reported. The structure of the samples are characterized by elemental analysis, FT-IR spectroscopy, X-ray diffraction, and NMR spectrometry. Cellulose carbamates with a nitrogen content of 0.651-2.427% are obtained by microwave heating at 255 W for 2-5 min. With the introduction of carbamate groups, the hydrogen bonding and crystalline structure of the native cellulose are partially destroyed. The products retain the cellulose I crystalline form of the native cellulose, and display good solubility in NaOH solutions.