Nanoemulsions and Nanolatexes Stabilized by Hydrophobically Functionalized Cellulose Nanocrystals

Carboxylic acid cellulose nanocrystals (CNC-COOHs) that have been covalently functionalized (via peptide coupling chemistry) with a range of different hydrophobic groups have been investigated as nanoparticle surfactants to stabilize styrene-in-water nanoemulsions. It is shown that the size and stability of these nanoemulsions depend on both the amount of surface carboxylic acid groups as well as the amount and type of hydrophobic alkyl groups on the CNC surface. Two different biosources for the CNCs, microcrystalline cellulose (MCC) and Miscanthus x. Giganteus (MxG), were investigated to see the effect that the CNC aspect ratio has on these nanoemulsions. Stable oil-in-water (o/w) Pickering emulsions with particle diameters of only a few hundred nanometers can be accessed using these hydrophobic functionalized CNCs, and the resulting emulsions can be polymerized to access nanometer sized latexes. The hydrophobic/hydrophilic balance of the functionalized CNCs was found to be critical to lower the interfacial tension between oil and water, which allowed access to stable emulsions with droplet diameters <1 μm. The ability to stabilized nanosized emulsions and latexes extends the potential of CNCs as green surfactants for numerous technological applications, such as food, cosmetics, drug delivery systems, and coatings.