Effect of solvent exchange on the solid structure and dissolution behavior of cellulose.

Effects of solvent exchange and milling on the solid structure of cellulose were investigated, using small- and wide-angle X-ray scattering and solid-state NMR. The solvent exchange facilitated the dissolution of cellulose in LiCl/DMAc with no change of the crystalline structure of cellulose. In contrast, the milling never facilitated the dissolution of cellulose, though the crystalline structure was almost destroyed. These facts show that the crystalline structure of cellulose hardly affects the dissolution in LiCl/DMAc. The fractal dimensions determined by the small-angle X-ray scattering measurements were increased by the solvent exchange, suggesting that the aggregation state of the cellulose microfibril is affected. It was also suggested by the NMR (1)H spin relaxation time measurements that the solvent exchange enhances the molecular mobility of cellulose and shortens the characteristic length along the microfibril, which allows easier access of the solvent molecule to cellulose.