CELLULOSE DERIVATIVES WITH LOW DS .1. A NOVEL ACYLATION SYSTEM

The acylation of cellulose in homogeneous phase (2% concentration in N ,N-DMAc/LiCl-9%) with acid anhydrides and carboxylic acids was accompl ished using N,N-dicyclohexylcarbodiimide (DCC) and 4-pyrrolidinopyridi ne (PP). This activation mixture assures retention of homogeneous phas e by keeping all components in solution. DCC serves as sacrificial act ivator in the reaction with acid anhydrides and carboxylic acids, maki ng it possible to achieve efficient modification with only a modest ex cess of reagent (0 to approximately 50% based on DS). DCC may be recyc led and regenerated. The method was used to prepare cellulose propiona tes to stearates with DS ranging between <0.1 and 2.5. Both type and d egree of substitution was found to influence solubility. The OH groups in positions C6 and C2 were favored to an equal degree over those in C3, and this varied from around 1 (i.e. equal reactivity as C3) to 3 d epending on DS.