Molecular characterization of thermoreversibility and temperature dependent physical properties of cellulose solution in N,N-dimethylacetamide and lithium chloride

The effects of temperature on the physical properties of the cellulose solutions in N,N-dimethylacetamide (DMAc) containing 9 (solvent-9) or 6 wt% (solvent-6) lithium chloride (LiCl) were investigated over the temperature range of 30 to 80 A degrees C. The cellulose solution exhibited a lower critical solution temperature (LCST) behavior over the temperature range observed. The content of LiCl affected the thermoreversible LCST behavior of cellulose solutions, which was almost thermoreversible over the temperature range of 30 to 80 A degrees C for solvent-9 and 30 to 50 A degrees C for solvent-6. The partial thermoreversibility of cellulose chain between 60 and 80 A degrees C in solvent-6 could be explained by increased intramolecular interactions between cellulose molecules with increasing temperature. The thermoreversible LCST behavior of cellulose solution for solvent-9 was further supported by dynamic light scattering measurement which also verified the larger decrease of cellulose chain dimensions in solvent-6 between 60 and 80 A degrees C. The cellulose solutions in DMAc/LiCl exhibited little thermal degradation in the short-term aging between 30 and 80 A degrees C. However, they produced a little thermal degradation in the long-term aging between 80 and 100 A degrees C.