Distribution and Quantification of Diverse Functional Groups on Phosphorylated Nanocellulose Surfaces

Area of Science:

• Materials Science
• Polymer Chemistry
• Nanotechnology

Background:

• Cellulose nanofibers (CNF) are advanced nanomaterials with growing applications.
• Phosphorylated CNF offers enhanced functionality but its structural details are not fully understood.
• Clarifying the structure of phosphorylated CNF is crucial for optimizing its properties and applications.

Purpose of the Study:

• To elucidate the chemical structures and ionic functional group distribution on phosphorylated CNF surfaces.
• To investigate the impact of phosphorylation time on the types and proportions of phosphate groups.
• To determine the regioselectivity of the phosphorylation reaction on cellulose.

Main Methods:

• Utilized liquid-state nuclear magnetic resonance (NMR) spectroscopy on colloidal dispersions of phosphorylated CNF.
• Analyzed the types and proportions of monophosphate, polyphosphate, and cross-linked phosphate groups.
• Investigated the substitution patterns at different positions of the cellulose molecule.

Main Results:

• Identified monophosphate, polyphosphate, and cross-linked phosphate groups on phosphorylated CNF.
• Observed an increase in polyphosphate groups with longer phosphorylation times, reaching approximately 30%.
• Demonstrated regioselective phosphorylation at the C2 and C6 positions with no significant difference in substitution degree.

Conclusions:

• The phosphorylation of CNF introduces a variety of phosphate groups, with polyphosphates becoming more prevalent over time.
• The phosphorylation process is regioselective, primarily occurring at the C2 and C6 positions of cellulose.
• This detailed structural understanding of phosphorylated CNF will aid in the development of novel functional materials.