NMR characterization of cellulose acetate: Mole fraction of monomers in cellulose acetate determined from carbonyl carbon resonances.

Cellulose acetate (CA) samples with varying degrees of substitution were prepared via homogeneous acetylation in 1-butyl-3-methylimidazolium chloride ([BMIM]Cl) and by the acid-hydrolysis of cellulose triacetate in acetic acid. Quantitative analysis of the 13C NMR spectra facilitated the assignment of the carbonyl carbon shifts of the 2-mono-, 3-mono-, 6-mono-, 2,3-di-, 2,6-di-, 3,6-di-, and 2,3,6-tri-substituted anhydroglucose units (AGUs), and the determination of the mole fraction of 7 AGUs and unsubstituted AGU in the CA chains. This shed some light on the mechanism of CA production in homogeneous reaction systems. In addition, comparison of the mole fractions of the 8 AGUs suggested that the acetone solubility of CA strongly related to the AGU composition.