Polyphenol-induced cellulose nanofibrils anchored graphene oxide as nanohybrids for strong yet tough soy protein nanocomposites.

Network-nanostructured cellulose nanofibrils (CNFs) is a promising template onto which to anchor and expand 2D sheets. It is still a huge challenge to regulate the dispersion/interface toward strong yet tough hybrid materials. This paper reports a novel design for interface anchoring GO nanosheets with TEMPO-oxidized CNFs (TA@rGO-CNFs) that is induced by the self-polymerization of catecholamine-based tannic acid (TA). The high-functionality TA@rGO-CNFs nanohybrids were investigated as both physical and chemical cross-linkers to the natural plant-derived soy protein isolate (SPI) based films, which facilitate multiple interfacial adhesion and a covalent network between the SPI matrix and TA@rGO-CNFs nanosheets bearing poly (tannic acid) (PTA) adhesion layers. As expected, remarkable improvement in tensile strength (up to 280.7%) and toughness (up to 258.3%) was achieved simultaneously in the resulting nanocomposites due to the efficient energy dissipation mechanisms derived from the synergistic interfacial interactions between TA@rGO-CNFs-"load distributers" and the SPI matrix. The nanocomposites also showed favorable gas barrier behavior (55% reduction) and water-resistance properties. The proposed method may represent a facile and environmentally-friendly approach to integrate multi-nanoscale building blocks into biopolymers with strong yet tough mechanical properties.