Counterion-Dependent Material Properties of Phosphorylated Nanocellulose

The material properties of cellulose nanofibers (CNFs) are governed by the surface chemical structure of the fibers. The chemical structure-property relationships for mono-valent carboxylated CNFs are well understood. Here, we report the basic sheet properties of divalent phosphorylated CNFs with different phosphorus contents and counterion types. All examined sheet properties, including conditioned and wet tensile properties, electrical resistivities, and fire-retardant properties of the CNF sheets, were greatly enhanced by the counterion exchange from the initial sodium ions to calcium or aluminum ions. The phosphorus content had significant influences only on the conditioned tensile and fire-retardant properties. In comparison to CNF sheets with monovalent carboxy groups, the CNF sheets with divalent phosphate groups were superior in terms of their wet tensile properties and fire-retardant properties. Our research shows that the combination of the divalent phosphate introduction and counterion exchange provides a successful strategy for the practical application of CNF sheets as antistatic materials and flexible substrates for electronic devices.

Automated summary

We report the basic sheet properties of divalent phosphorylated cellulose nanofibers (CNFs) with different phosphorus contents and counterion types. The counterion exchange from sodium ions to calcium or aluminum ions greatly enhances all examined sheet properties of CNF sheets. The phosphorus content only has significant influences on conditioned tensile and fire-retardant properties. Compared to CNF sheets with monovalent carboxy groups, CNF sheets with divalent phosphate groups are superior in terms of wet tensile properties and fire-retardant properties.