bm400219u_si_001.pdf (40.23 MB)
Isolation of Thermally Stable Cellulose Nanocrystals by Phosphoric Acid Hydrolysis
journal contribution
posted on 2013-04-08, 00:00 authored by Sandra Camarero Espinosa, Tobias Kuhnt, E. Johan Foster, Christoph WederOn account of their intriguing mechanical
properties, low cost,
and renewable nature, high-aspect-ratio cellulose nanocrystals (CNCs)
are an attractive component for many nanomaterials. Due to hydrogen
bonding between their surface hydroxyl groups, unmodified CNCs (H-CNCs)
aggregate easily and are often difficult to disperse. It is shown
here that on account of ionic repulsion between charged surface groups,
slightly phosphorylated CNCs (P-CNCs, average dimensions 31 ±
14 × 316 ± 127 nm, surface charge density = 10.8 ±
2.7 mmol/kg cellulose), prepared by controlled hydrolysis of cotton
with phosphoric acid, are readily dispersible and form stable dispersions
in polar solvents such as water, dimethyl sulfoxide, and dimethylformamide.
Thermogravimetric analyses reveal that these P-CNCs exhibit a much
higher thermal stability than partially sulfated CNCs (S-CNCs), which
are frequently employed, but suffer from limited thermal stability.
Nanocomposites of an ethylene oxide–epichlorohydrin copolymer
and H-CNCs, S-CNCs, and P-CNCs were prepared, and their mechanical
properties were studied by dynamic mechanical thermal analysis. The
results show that P-CNCs offer a reinforcing capability that is comparable
to that of H-CNCs or S-CNCs.