Polyphenols, such as tannic acid, are widely distributed in plant tissues where they are involved in diverse biological functions including structural support, pigmentation, chemical defense, and prevention of radiation damage. The high catechol and gallic acid content of plant polyphenols recently received attention in the context of nanoparticle surface modification, as catechols are known to strongly bind to surfaces and are prominent constituents of marine polyphenolic-protein adhesives. Furthermore, tannic acid is known to form complexes with a wide range of macromolecules including carbohydrates, proteins, enzymes and other synthetic polymers. This work presents two examples of the synergistic interactions between tannic acid and cellulose nanocrystals (CNCs):<br/>1. Hydrophobic modification of CNCs – CNCs are promising renewable nanoparticles with unique mechanical properties, however, the major challenge limiting the design of commercial products is the inability to disperse them in non-polar materials (both liquids and solids) due to the innate hydrophilicity of cellulose. We demonstrate a simple water-based modification route where a CNC suspension is mixed with tannic acid (the primer) followed by the addition of alkylamines or alkanethiols (the hydrophobe). Specifically with tannic acid and dodecylamine we achieve CNCs that are well dispersed in toluene but retain the positive characteristics of CNCs.<br/>2. Dried and redispersible oil-in-water emulsions – The addition of tannic acid enables the freeze-drying of Pickering emulsions stabilized by CNCs and water-soluble cellulose derivatives, without emulsion droplet coalescence or oil leakage. The dried emulsions have oil contents of 94 wt.% and can be readily redispersed in water with gentle shaking (with the same oil droplet size as before drying). We view this as a new encapsulation method to protect oils and oil-soluble compounds and believe that these processing abilities will likely extend the use of these surfactant-free, “green” and potentially edible emulsions to new food, cosmetic and pharmaceutical applications.

Tannic acid – A transformative additive when combined with cellulose nanocrystals: From hydrophobic nanoparticles to dried oil powders

253rd National Meeting (2017)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.