Acetylation of Xanthan Gum in Ionic Liquid

In this paper, we report acetylation of xanthan gum using acetic anhydride in an ionic liquid solvent, 1-butyl-3-methylimidazolium chloride (BMIMCl). Xanthan gum was dissolved with BMIMCl [2 % (w/w)] and the reaction was carried out in the presence of acetic anhydride (five equiv. for hydroxy groups in a repeating unit) with stirring the solution at elevated temperatures. The structures of xanthan gum acetates were confirmed by the H-1 NMR and IR spectra. The degree of acetylation (DA) values determined by the H-1 NMR analysis increased with the higher reaction temperatures. The thermal gravimetric analysis (TGA) indicated the enhancement of thermal stability by acetylation. Furthermore, the TGA as well as differential scanning calorimetric (DSC) analysis of the products suggested the presence of the highly and less acetylated segments in a xanthan gum chain. The DSC profile of the product with the high DA value also exhibited a small endothermic peak, which might potentially be ascribed to the melting temperature.