High throughput disassembly of cellulose nanoribbons and colloidal stabilization of gel-like Pickering emulsions

We introduce a strategy to disintegrate cellulose microfibrils present in the cell walls of plant fibers. The process includes impregnation and mild oxidation followed by ultrasonication, which loosens the hydrophilic planes of crystalline cellulose while preserving the hydrophobic ones. The resultant molecularly-sized cellulose structures (cellulose ribbons, CR) retain a length of the order of a micron (1.47 +/- 0.48 mu m, AFM). A very high axial aspect ratio is determined (at least 190), considering the CR height (0.62 +/- 0.38 nm, AFM), corresponding to 1-2 cellulose chains, and width (7.64 +/- 1.82 nm, TEM). The new molecularly-thin cellulose proposes excellent hydrophilicity and flexibility, enabling a remarkable viscosifying effect when dispersed in aqueous media (shear-thinning, zero shear viscosity of 6.3 x 105 mPa.s). As such, CR suspensions readily develop into gel-like Pickering emulsions in the absence of crosslinking, suitable for direct ink writing at ultra-low solids content.

Automated summary

We have developed a strategy to break down cellulose microfibrils in plant fiber cell walls. By impregnation, mild oxidation, and ultrasonication, we obtained molecularly-sized cellulose structures (cellulose ribbons) that maintain hydrophilic and hydrophobic properties. These cellulose ribbons exhibit excellent hydrophilicity and flexibility, allowing them to form gel-like Pickering emulsions suitable for direct ink writing at ultra-low solids content.