An investigation in solution acetylation of cellulose by microscopic techniques

The solution acetylation process of cellulose has been investigated by means of scanning electron and transmission microscopic techniques. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) revealed the different morphologies of cellulose acetates, which were prepared at different temperatures. Simply, for the high-temperature acetylation( 90 degrees C), the reagents progressed in a linear manner, consisting of the formation of continuous micropores, from the surface into the interior of the supermolecular structure. In contrast, for the low-temperature acetylation (45 degrees C), the reaction took place only through the segregated micropores on the surface of cellulose. As a result, the successive layers and, subsequently, fragmented platelets of the acetylated surface were solubilized in the reaction medium, and a viscous solution was eventually obtained. The experimental conformity between the SEM and TEM results provided valuable information in support of different solution acetylation mechanisms at low and high temperatures. (C) 1997 John Wiley & Sons, Inc