Tert-Butanol as a Structuring Agent for Cellulose Nanocrystal Fluids and Foams.

Nanocelluloses are uniquely valued for their high surface area and controllable assembly. This study elucidates the assembly of cellulose nanocrystals (CNCs) in tert-butanol (TBA) and water mixtures. We emphasize the influence of TBA on the structure of suspensions and freeze-dried foams. Although the length-scale of CNC organization is large relative to water-TBA structures, adding more than 30 wt % TBA shifted ordered CNC packing into an isotropic network. The change was attributed to the disruption of ionic interactions and adsorption of TBA to hydrophobic CNC interfaces; manifesting as a 5-fold increase in viscosity at 50 wt % TBA content. The freeze-dried foams' morphology was transformed due to TBA-modulated crystal growth during the freezing process. This led to the intriguing capability to control foams' mechanical strength and surface area, achieving up to 3 and 15-fold increases, respectively. The investigations highlight TBA's potential as a structuring agent in solvent-mediated design of nanomaterial systems.