Preparation of Cellulose Succinates with High Degree of Substitution in Solvent System [C4mim]Cl/DMSO

Homogeneous derivatization of cellulose was investigated with succinic anhydride (SA) in a solvent system containing 1-butyl-3-methylimidazolium chloride ionic liquid ([C(4)mim]Cl) and dimethylsulfoxide (DMSO) using iodine, N-bromosuccinimide (NBS), and 4-dimethylaminopyridine (DMAP) as a catalyst. The results showed that the high degree of substitution (DS) of modified cellulose significantly increased from 0.24 without any catalysts to 0.84, 2.31, and 2.34 under same conditions except with I-2, NBS, and DMAP, respectively, as a catalyst. The possible mechanism of succinoylation catalysed with different catalysts was discussed. Fourier transform infrared and solid-state cross-polarization/magic angle spinning C-13 NMR spectroscopies also provided evidences of catalyzed homogeneous succinoylation reaction. The results indicated that iodine, NBS, and DMAP could effectively improve the succinoylation efficiency of cellulose in [C(4)mim]Cl/DMSO.