Synthesis of cationic hemicellulosic derivatives with a low degree of substitution in dimethyl sulfoxide media

A series of water-soluble cationic 2-hydroxylpropyltrimethylammonium hemicellulosic derivatives with low average degrees of substitution (DS's) were prepared by the incorporation of the cationic moiety 2,3-epoxypropyltrimethylammonium chloride (ETA) onto the backbone of hemicelluloses in the presence of NaOH as a nucleophilic catalyst in homogeneous dimethyl sulfoxide (DMSO) media. The dependence of the homogeneous reaction on the different affecting factors was investigated. The average DS was calculated from the N/C ratio in the products and from the weight gain. The degree of substitution determined by the nitrogen content (DSN) values up to 0.25 in a one-step synthesis of the etherified hemicelluloses could be controlled by the adjustment of the amount of solvent used and the molar ratio of NaOH or ETA to the anhydromonomer units in the hemicelluloses. The structure of the cationic hemicellulosic derivatives formed was determined by Fourier transform infrared spectroscopy and further confirmed with solution-state C-13-NMR spectroscopy. In comparison, no significant degradation of the hemicellulosic derivatives occurred during the etherification of the polymers in the homogeneous DMSO system. (c) 2008 Wiley Periodicals, Inc.