Enhancement of the Chemical Reactivity of Native Cellulose via the Amorphous State, Prepared Using Amine/Inorganic Salt Solvents

Highly reactive cellulose is prepared by dissolving native cellulose in amine/inorganic salt solvents followed by precipitation with a nonaqueous organic liquid. The chemical reactivity of the resultant amorphous cellulose is compared with those of the original natural cellulose and conventional amorphous cellulose prepared by ball‐milling. The present amorphous celluloses prepared from microcrystalline cellulose (MCC; viscosity‐average degree of polymerization DP V 233; crystallinity index CI 0.80) and filter paper (FP; DP V 2670; CI 0.72) are acetylated with acetic anhydride catalyzed by sulfuric acid at 0°C and 25°C. The degree of acetylation (DS) of the products is compared with those of the corresponding original cellulose and conventional amorphous cellulose, which reveals that the present amorphous celluloses greatly enhance susceptibility to acetylation. Notably, at 0°C, both the original MCC and FP undergo almost no acetylation, whereas the corresponding amorphous forms give the acetates with DS 3.0 and 2.3, respectively. The results suggest that such high reactivity is due to fewer hydrogen bonds between hydroxyl groups. The IR spectrum of the present amorphous cellulose after H–D exchange in deuterium oxide demonstrates that OD absorption is greater than that in the spectrum of the native cellulose subjected to the same H–D exchange process.