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 accomplished using N,N-dicyclohexylcarbodiimide (DCC) and 4-pyrrolidinopyridine (PP). This activation mixture assures retention of homogeneous phase by keeping all components in solution. DCC serves as sacrificial activator in the reaction with acid anhydrides and carboxylic acids, making it possible to achieve efficient modification with only a modest excess of reagent (0 to approximately 50% based on DS). DCC may be recycled and regenerated. The method was used to prepare cellulose propionates to stearates with DS ranging between <0.1 and 2.5. Both type and degree 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 depending on DS.