Partial silylation of cellulose with predictable degree of silylation - stoichiometric silylation with hexamethyldisilazane in ammonia

The silylation of cellulose with hexamethyldisilazane (HMDS) in liquid ammo nia at elevated temperature has been extended to the synthesis of partly si lylated trimethylsilylcellulose. Predictable degrees of silylation (DS) wer e obtained either with excess ammonia or in a nearly 1 : 1 ratio of NH3/AGU (anhydroglucose unit) or with toluene as co-solvent. Complete reaction of the silylating agent allows to adjust the DS directly by simple variation o f the ratio of OH groups to trimethylsilyl groups of the silylating agent. With chlorotrimethylsilane more than the stoichiometric amount of silylatin g agent is required to obtain a desired DS and the work up is more tedious. A simple method to determine the DS of trimethylsilylcellulose based on in frared spectroscopy is proposed. It is applicable to cellulose with a DS gr eater than 1.3.