Different rheological behaviours of cellulose/tetrabutylammonium acetate/dimethyl sulfoxide/water mixtures

Tetrabutylammonium acetate (TBAA) solution in dimethyl sulfoxide (DMSO) can dissolve cellulose efficient at a mild condition and it seems to have favorable properties for cellulose molding applications, e.g. fiber spinning. However, if water or other hydrogen bond donors are present, the solvent's ability to dissolve cellulose is greatly reduced. A non-solvent (water) post-added to the cellulose/TBAA/DMSO solutions caused significant changes in flow properties. Specifically, the rheological behaviours of distinct phases formed in 6–8%(w/w) cellulose/TBAA/DMSO solutions due to the addition of water was investigated. With the water concentrations increased, a sol–gel transition had been detected. The Cox–Merz rule and Cross model have been used to fit the rheological data. We explain the sol–gel transformation in cellulose/TBAA/DMSO/water solutions by percolation theory. Meanwhile, a mechanism of cellulose aggregation and the sol–gel transitions have been proposed: water can effectively break the cellulose–Ac− H-bonds and lead to the formation of cellulose–cellulose H-bonds, which grow the aggregation of cellulose, form a network structure in the whole sample and then result in gelation. Sol-gel transition of cellulose/tetrabutylammonium acetate/dimethyl sulfoxide solutions with different water concentrations.