Supramolecular structure characterization of cellulose II nanowhiskers produced by acid hydrolysis of cellulose i substrates

Cellulose II nanowhiskers (CNW-II) were produced by treatment of microcrystalline cellulose with sulfuric acid by both controlling the amount of H 2SO 4 introduced and the time of addition during the hydrolysis process. The crystalline structure was confirmed by both XRD and 13C CP-MAS NMR spectroscopy. When observed between crossed polarizers, the cellulose II suspension displayed flow birefringence and was stable for several months. The CNW-II nanowhiskers were significantly smaller than the cellulose I nanowhiskers (CNW-I) and had a rounded shape at the tip. The CNW-II average length and height were estimated by AFM to be 153 ± 66 and 4.2 ± 1.5 nm, respectively. An average width of 6.3 ± 1.7 nm was found by TEM, suggesting a ribbon-shape morphology for these whiskers. The average dimensions of the CNW-II elementary crystallites were estimated from the XRD data, using Scherrer's equation. A tentative cross-sectional geometry consistent with both XRD and NMR data was then proposed and compared with the geometry of the CNW-I nanowhiskers. © 2012 American Chemical Society.