We investigated the state of cellulose that was dissolved in ionic liquid (IL) consisting of 1-methyl-3-propylimdiazolium cation ([C 3 mim] + ) paired with acetate ([OAc] − ), dimethylphospate ([DMP] − ), or chloride (Cl − ) anions using wide-angle X-ray scattering (WAXS), particularly focusing on the high cellulose concentration region (10−80 mol %). The anion species considerably altered the WAXS pattern of the cellulose/IL mixtures. [C 3 mim][OAc] deconstructed cellulose crystal structure up to the 40 mol % cellulose concentration. Similar to the previously reported cellulose/1-ethyl-3-methylimidazolium acetate system ([C 2 mim][OAc]), the mixtures of cellulose/[C 3 mim]-[OAc] at 25−60 mol % induced a low angle peak, which corresponds to the self-assembly of the system. For [C 3 mim]-[DMP] and [C 3 mim]Cl mixtures, sharp Bragg peaks were observed, which demonstrated the formation of the complex crystal of cellulose/IL. The presence of moisture eventually deconstructed these crystal structures; while for [C 3 mim]Cl, an intermediate complex crystal containing H 2 O molecules emerged. This work contributes to understanding the cellulose state dissolved in IL at high concentrations and to the development of crystal engineering on this most abundant and recalcitrant biopolymer.

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