Structure Formation in Dense Gels of Cellulose and Ionic Liquid

Cellulose regeneration from solutions is commonly used and essential for applications that require rearrangement of cellulose molecules from their native structures, whereas the transient intermediate state of cellulose condensates during regeneration is poorly understood. In this study, dense gels of cellulose and ionic liquid (IL) with high cellulose content have been prepared by initially vacuum evaporating the solvent DMSO from ternary molecular solutions of cellulose, yielding a dense gel of cellulose/IL with a molar ratio of cellulose sugar units to IL at ca. 1:3. Further successive removal of IL results in a series of nearly equilibrated binary mixtures of cellulose/IL approaching neat cellulose. Small and wide angle x-ray scattering (SAXS and WAXS) indicate multiscale structures in the gels, where the local crystalline order shows a unique lattice structure, and the mesoscale structure has a characteristic correlation length that increases with the IL content. The temperature and composition dependencies of the multiscale gel structures have been investigated. Dynamic mechanical properties have also been studied.