On the dissolution state of cellulose in aqueous tetrabutylammonium hydroxide solutions

Abstract

We have characterized the dissolution state of microcrystalline cellulose (MCC) in aqueous 40 wt% tetrabutylammonium hydroxide (TBAH) using a combination of light and small angle X-ray scattering, up to 0.1 g cm⁻³. In dilute solutions, cellulose–cellulose interactions are repulsive, as seen by a positive second virial coefficient. Above 0.04 g cm⁻³, interactions shift from repulsive to be effectively attractive and cellulose begin to form aggregates that can be modelled as mass fractal clusters. The small angle X-ray scattering data also indicate that cellulose is preferentially solvated by TBA⁺ ions. We propose that the apparent shift in effective interactions is due to a phase transition where less soluble cellulose II precipitates while cellulose I still dissolves.