Solvent-free acetylation of bacterial cellulose under moderate conditions

Bacterial cellulose preserving the microfibrillar morphology was partially acetylated by the solvent-free acetylation method using acetic anhydride in the presence of iodine as a catalyst. The results showed that within the range of catalyst amounts studied, the overall degree of substitution increased as the amount of iodine used increased. We also found that the reaction time and temperature had an active influence on the extent of acetylation. X-ray diffraction profiles indicated that acetylation proceeded from the surface to the interior of BC nanofibers, and scanning electron microscopy images revealed that even low levels of acetylation were effective to make the nanofibers separated from each other. NMR analysis indicated the regio-nonselective reactivity of the OH groups in the glucose units in the acetylation process. The obtained acetylated BC membrane shows more hydrophobic surface and good mechanical properties which is in favor of enhancing the hydrophobic non-polar polymeric matrix.