Sterically stabilized cellulose nanocrystals by polyetheramine grafting: preparation, characterization and colloidal stability in the presence of salts

Sterically stabilized cellulose nanocrystals (CNCs) were obtained by hydrolysis of cotton wool with aqueous hydrochloric acid, subsequent TEMPO-mediated oxidation, followed by amidation of the resulting carboxylated CNCs with a bifunctional polyetheramine (Jeffamine ED-2003) using EDC-NHS coupling. Covalent attachment of polyetheramine onto the carboxylated CNCs was confirmed by infrared spectroscopy, solution-state NMR spectroscopy, and elemental analysis. It was shown that amide graft formation competes with the grafted N -acylurea by-product of amidation, with a molar ratio between the amide and the N-acylurea being close to unity. PEA grafting resulted in a change in CNC thermal behavior, resulting in a two-step thermal degradation and melting, behavior similar to pure polyetheramine. The obtained polyetheramine-grafted CNCs were found to form stable colloidal aqueous suspensions over a broad range of concentrations of the kosmotrope sodium chloride, in the presence of various other cations and anions, and in various physiologically relevant solutions. This feature makes these materials, and protocols, interesting for applications where stability is required in high-ionic strength media.