Cellulose dissolution in aqueous lithium bromide solutions

A new all-aqueous process of the dissolution/regeneration of cellulose was developed. Cellulose was completely dissolved in the 54-60 wt% lithium bromide aqueous solutions in the temperature range of 110-130 A degrees C within a dissolution time of 1 h. Then, the cellulose was directly regenerated from the solution by cooling down to approximately 70 A degrees C and removing the salts with water, yielding a translucent gel. The cellulose gel was not significantly chemically decomposed even though some decrease of the degree of polymerization occurred during the dissolution/regeneration of cellulose. The X-ray diffraction analysis demonstrated that the dissolution/regeneration of cellulose induced a crystalline structural change from cellulose I to cellulose II, confirming the complete loss of the original cellulose structure. The cellulose gel had highly porous three-dimensional networks composed of fairly long cellulose fibrils interconnected with one another. The dissolution/regeneration of cellulose in aqueous lithium bromide solutions offers new and important options for cellulose-based materials.