Structural and thermal characterization of lauroylated hemicelluloses synthesized in an ionic liquid

Chemical modification provides an efficient way to obtain novel biomaterials from abundant biomacromolecules. In this case, lauroylated hemicelluloses (LH) with degree of substitutions (DS) between 0.43 and 1.82 were synthesized in 1-butyl-3-methylimidazolium chloride ([BMIM]Cl) ionic liquid. The influence of reaction parameters including the molar ratio of lauroyl chloride (LC) to anhydroxylose units in hemicelluloses (0.5:1-3:1), reaction temperature (80-90 °C), and reaction time (15-90 min) was studied. The results indicated that homogeneous modification was successfully conducted and highly substituted hemicelluloses esters were obtained. In comparison, the hemicellulose and LH were characterized by both degradative methods such as thermal analysis (TGA/DTG), and non-degradative techniques such as Fourier transform infrared (FT-IR), 13C nuclear magnetic resonance (NMR) spectroscopy, and scanning electron microscopy (SEM). It was found that a significant degradation of the hemicellulose polymers occurred during lauroylation with the increase of the molar ratio, time, and temperature. The thermal stability of LH was lower that of the native hemicelluloses, and the morphological properties of hemicellulose were significantly changed after the chemical modification.