Esterification and hydrolysis of cellulose using oxalic acid dihydrate in a solvent-free reaction suitable for preparation of surface-functionalised cellulose nanocrystals with high yield

A one-pot esterification and hydrolysis of cellulose was carried out by treating cellulose fibres with molten oxalic acid dihydrate. Each cellulose oxalate had a free carboxyl content above 1.2 mmol. g(-1) and an average molecular weight of approximately 40 kDa. Aqueous suspensions of the oxalates were sonicated to prepare cellulose nanocrystals with a gravimetric yield of 80.6%.