Synthesis of cellulose acetate propionate and cellulose acetate butyrate in a CO2/DBU/DMSO system

The reversible reaction of the hydroxyl groups in cellulose with CO2 in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) results in a rapid and effective derivative dissolution of cellulose in DMSO, by which a series of cellulose acetate propionate (CAP) and cellulose acetate butyrate (CAB) with various degrees of substitution (DS) were synthesized controllably without adding external catalysts. Wherein DBU not only achieves the dissolution of cellulose, but also acts as an efficient organocatalyst for the subsequent cellulose derivatization. The DS of CAB and CAP can be tuned by changing the feed molar ratio of propionic (butyric) anhydride/acetic anhydride and the reaction temperature. The structural and thermal properties of the products were characterized by several analytical techniques including NMR, FT-IR, and TGA. The CO2/DBU/DMSO dissolution system provides a new platform for controllable synthesis of mixed cellulose esters with high efficiency under mild conditions.