Rapid homogeneous lauroylation of wheat straw hemicelluloses under mild conditions

Hemicellulose-based hydrophobic biomaterials with degrees of substitution ranging from 0.46 to 1.54 were synthesized under mild conditions in homogeneous media (N,N-dimethylformamide-lithium chloride) by reacting the native wheat straw hemicellulosic polymers with lauroyl chloride using 4-dimethylaminopyricline as a catalyst. Other catalysts such as N-bromosuccinimide, N-methyl pyrrolidine, N-methyl pyrrolidinone. and pyridine were also investigated. Under optimum reaction conditions (2 equiv of lauroyl chloride and triethylamine per hydroxyl group, 5% 4-dimethylaminopyridine, 40 degrees C, 35 min), a high DS value of 1.54 was obtained. The biomaterials were characterized by FT-IR spectroscopy and C-13 NMR spectroscopy as well as by thermal analysis. The results showed that the lauroylation occurred preferably at the C-3 hydroxyl group of beta-D-Xylp units in the hemicelluloses, and the thermal stability of the hydrophobic polymers increased by esterification. (C) 2008 Elsevier Ltd. All rights reserved.