Water regulates ionic liquid solvation and can fine-tune the rheological behavior of dissolved cellulose

• The presence of H 2 O in ionic liquid (IL) lowers cellulose’s capacity to dissolve • Cellulose fibrils are seen in water-IL mixture that affect rheology • The IL mediated precipitates are still relatively stiff and strong biopolymers Water contamination is difficult to control in the field given ambient humidity levels, rain, dew, and the hygroscopic quality of polar ionic liquids (ILs) like 1,8-Diazabicyclo[5.4.0]undec-7-ene [DBUH][-OAc], a well-characterized ionic liquid. With water, there is a H-bond competition between it and [DBUH][-OAc] suggesting that the overall solubility of cotton can be throttled by trace amounts of water thus throttling rheological measurements. Here, 5 wt% cotton was dissolved in [DBUH][-OAc] solutions in the presence of 0-20 wt.% water. Gravimetric analysis, rheology and microscopy on regenerated cotton fibers were conducted to characterize water’s influence on cotton dissolution. We confirmed the lower cellulose solubility with increasing water content. Roughly 7% w/w water was enough to essentially eliminate the IL solubility for cotton. Zero-shear viscosities of ∼10 -20 Pa-s were found for extracts of the neat solutions in IL at 60°C. Cotton fibers re-formed by syringe precipitation resulted in modulus values of ∼1-6 GPa and tensile strengths between 60-160 MPa.