Trifluoroacetic acid as an effective dispersing medium for cellulose nanocrystals

While reports of innovations in the production of cellulose nanocrystals (CNCs) are common, strategies for dispersing CNCs in various media, on which many practical applications depend, are limited. Although the suspension of surface-modified cellulose nanoparticles in water and other media has been described, dispersion of native CNCs in common solvents is challenging. Here, we show that trifluoroacetic acid, a volatile liquid which is miscible both with water and organic solvents, can be used to prepare metastable, turbid suspensions of native CNCs that clarify and stabilize over the course of several hours. These suspensions were characterized by imaging (TEM/AFM), thermal analysis (TGA), spectroscopic analysis (FT-IR and NMR), and evolution of crystallinity (XRD). Composite films could be made from these suspensions and waste poly(ethylene terephthalate) (PET) by simple evaporation of the TFA medium and subsequent washing with water. These films were observed to be hydrophilic and porous, and were characterized by SEM and porosimetry.