Solubility of a High Molecular-Weight Bacterial Cellulose in Lithium Chloride/N,N-dimethylacetamide Solution

High molecular-weight bacterial cellulose (BC) was found to be soluble in a lithium chloride/N,N-dimethylacetamide (LiCl/DMAc) solvent system with a maximal concentration of 3 wt% if an activation procedure was performed beforehand. The granular BC was not favored and had to be ground to powders before dissolution. To facilitate subsequent dissolution, an activation procedure consisting of stewing the BC samples at 45°C–50°C in DMAc containing dissolved KMnO4 was adopted. It was found that a swelling temperature of 45°C was preferred, for about 4 h, but continuous, constant temperature heating during dissolving procedure was unfavorable, possibly due to the instability of the intermediate complex formed between the Li+ ion and the carbonyl oxygen of DMAc. However, the BC sample would be gradually dissolved if placed at room temperature for a long enough time.