The Effect of Additives on the Viscosity and Dissolution of Cellulose in Tetrabutylphosphonium Hydroxide.

An electrolyte solution of tetrabutylphosphonium hydroxide (TBPH) in water can dissolve over 20 wt % of cellulose in minutes and therefore constitutes a promising alternative green solvent system compared to known imidazolium- or dimethylacetamide-based systems. Overcoming the disadvantage of the extremely high viscosity of TBPH/cellulose solutions can facilitate their use for various applications. In this study, the application of cosolvents for the reduction, and thus adjustability, of the viscosity is addressed. Even well-known antisolvents can be easily deployed, resulting in a dramatic drop in viscosity. High concentrations of cosolvents (excluding ethanol) are tolerated without precipitation of the dissolved cellulose. Furthermore, the effect of the cosolvents on the additional dissolution of cellulose is discussed. The amount of dissolved cellulose is quantified by C-13 NMR spectroscopy.