Because of lacking at thermoplasticity in cellulose, it requires solution states for molding processing. A typical example is viscose, which requires the use of a multiple solvent system including toxic. In order to improve the disadvantage, cellulose was dissolved in an ionic liquid mixed solvent and its solution characteristics were evaluated in the present study. Another method for imparting thermoplasticity to cellulose is chemical modification. Thus, an attempt was also made to acetylate cellulose in the ionic liquid mixed cellulose solution. Despite the fact that the solvent contains dimethyl sulfoxide, which causes the Pummerer rearrangement preventing esterification, cellulose acetate with a degree of substitution of 2.7 or higher was successfully prepared. The films were prepared by coagulation of the solution, and the film characteristics were evaluated by measuring their viscoelasticity. It was found that cellulose and cellulose acetate films obtained from the solvent have almost the same viscoelastic properties as commercially available ones. In addition, the solution characteristic in the ionic liquid mixed solvent of the obtained cellulose acetate was examined.
