Periodate Oxidation Followed by NaBH4 Reduction Converts Microfibrillated Cellulose into Sterically Stabilized Neutral Cellulose Nanocrystal Suspensions.

The periodate oxidation of microfibrillated cellulose followed by a reduction treatment was implemented to produce a new type of sterically stabilized cellulosic nanocrystals, which were characterized at the molecular and colloidal length scales. Solid-state NMR data showed that these treatments led to objects consisting of native cellulose and flexible polyols resulting from the oxidation and subsequent reduction of cellulose. A consistent set of data from dynamic light scattering, turbidimetry, transmission electron microscopy, and small-angle X-ray scattering experiments further showed that stable neutral elongated nanoparticles composed of a crystalline cellulosic core surrounded by a shell of dangling polyol chains were produced. The dimensions of these biosourced nanocrystals could be controlled by the degree of oxidation of the parent dialdehyde cellulose sample. The purely steric origin of the colloidal stability of these nanoparticles is a strong asset for their use under conditions where electrostatics no longer provides colloidal stability.