Synthesis of high molecular weight chitosan from chitin by mechanochemistry and aging

Chitosan can be obtained from the deacetylation of chitin. This process is however difficult and usually accompanied by depolymerization, affording low molecular weight chitosan. We report a novel path, relying on the combination of mechanochemistry and aging, to yield high molecular weight chitosan with minimal use of energy and solvent. This method is versatile and applicable to a number of chitin sources, including crude crustacean and insect shells, yielding deacetylation up to 98% and remarkably high molecular weights. Chitin deacetylation was studied by magic angle spinning nuclear magnetic resonance and molecular weight was estimated by viscometry. This process affords chitosan in a safer fashion and with less materials and energy usage compared to the classic hydrothermal one.