Synthesis of cellulose acetate propionate with controllable contents and distributions of acetyl and propionyl in the C2, C3 and C6 positions

In this work, during the synthesis and hydrolysis of cellulose acetate propionate (CAP), the research not only focused on the contents, but also the distributions of acetyl and propionyl groups in the different positions of anhydroglucose unit, i.e. C2, C3 and C6. It was investigated that cellulose propionylation was more difficult than acetylation, which required larger amounts of reagents. At the same temperature, the reaction rate constant of cellulose acetylation was much higher than that of propionylation. Furthermore, the partial degrees of propionyl substitution in CAP were 0.54, 0.54, and 0.48 for C2, C3, and C6. The contents of propionyl distributed on C2 and C3 positions were higher than that on C6 indicating that acetyl took the position of C6 preferentially. During the hydrolysis of CAP, the degrees of hydrolysis were 0.1 for acetyl and 0.3 for propionyl. Acetyl groups in the C6 position and propionyls in the C2 position were hydrolyzed much easier with the degrees of hydrolysis of 0.16 and 0.32, respectively. In addition, it has been investigated that hydroxyl groups in the C3 position exhibited the lowest reactivity during the synthesis of CAP, while acyl groups on C3 was also the hardest to be hydrolyzed.