Controlling Miscibility of the Interphase in Polymer-Grafted Nanocellulose/Cellulose Triacetate Nanocomposites

The miscibility at the interphase of polymer-grafted nanocellulose/cellulose triacetate (CTA) composite films was tailored using different casting solvents. The polymer-grafted cellulose nanofibrils were prepared by modifying surfaces of 2,2,6,6-tetramethylpiperidine-1-oxyl-oxidized nanocellulose with amine-terminated poly(ethylene glycol) (PEG). The PEG-grafted nanocelluloses were individually dispersed in dichloromethane, 1,4-dioxane, and N,N-dimethylacetamide. The PEG-grafted nanocellulose/CTA composite films were prepared by mixing the nanocellulose dispersion and CTA solution and subsequent casting-drying. The miscibility of PEG and CTA at the interphase of the composite was controlled by controlling the solvent, which was confirmed by dynamic mechanical analysis. All the composite films showed high optical transparency. However, the mechanical properties of the composites differed because of the difference in the PEG/CTA interfacial miscibility. The composite films with better PEG/CTA interfacial miscibility showed higher Young's modulus, strength, and toughness. This interfacial design technique paves the way to exploiting the reinforcing potential of highly transparent and hydrophobic surface-grafted nanocellulose/polymer composite materials.